Datasheet LT1399HV, LT1399, LT1398 Datasheet (Linear Technology)

FEATURES

■

300MHz Bandwidth on ±5V (A

■

0.1dB Gain Flatness: 150MHz (AV = 1, 2 and –1)

■

Completely Off in Shutdown, 0µA Supply Current

■

High Slew Rate: 800V/µs

■

Wide Supply Range:

= 1, 2 and –1)

V

±2V(4V) to ±6V(12V) (LT1398/LT1399)
±2V (4V) to ±7.5V (15V) (LT1399HV)

■

80mA Output Current

■

Low Supply Current: 4.6mA/Amplifier

■

Fast Turn-On Time: 30ns

■

Fast Turn-Off Time: 40ns

■

16-Pin Narrow SO/Narrow SSOP Packages

U

APPLICATIO S

LT1398/LT1399/LT1399HV

Low Cost Dual and Triple

300MHz Current Feedback

Amplifiers with Shutdown

U

DESCRIPTIO

The LT®1399 and LT1399HV contain three independent
300MHz current feedback amplifiers, each with a shut­down pin. The LT1399HV is a higher voltage version of the
LT1399. The LT1398 is a two amplifier version of the
LT1399.

The LT1398/LT1399 operate on all supplies from a single
4V to ±6V. The LT1399HV operates on all supplies from 4V
to ±7.5V.

Each amplifier draws 4.6mA when active. When disabled
each amplifier draws zero supply current and its output be­comes high impedance. The amplifiers turn on in only 30ns
and turn off in 40ns, making them ideal in spread spectrum
and portable equipment applications.

■

RGB Cable Drivers

■

LCD Drivers

■

Spread Spectrum Amplifiers

■

MUX Amplifiers

■

Composite Video Cable Drivers

■

Portable Equipment

TYPICAL APPLICATIO

3-Input Video MUX Cable Driver

CHANNEL

A

V

IN A

R

G

200Ω

V

IN B

R

G

200Ω

V

IN C

R

G

200Ω

EN A

+

1/3 LT1399

–

EN B

+

1/3 LT1399

–

EN C

+

1/3 LT1399

–

324Ω

324Ω

324Ω

SELECT

R

F

R

F

R

F

BC

97.6Ω

97.6Ω

97.6Ω

U

1399 TA01

75Ω

75Ω
CABLE

The LT1398/LT1399/LT1399HV are manufactured on Lin­ear Technology’s proprietary complementary bipolar pro­cess. The LT1399/LT1399HV are pin-for-pin upgrades to
the LT1260 optimized for use on ±5V/±7.5V supplies.

, LTC and LT are registered trademarks of Linear Technology Corporation.

Square Wave Response

V

OUT

OUTPUT

200mV/DIV

RL = 100Ω

= RG = 324Ω

R

F

f = 10MHz

TIME (10ns/DIV)

1398/99 TA02

1

LT1398/LT1399/LT1399HV

W

O

A

LUTEXI TIS

S

Total Supply Voltage (V+ to V–)

LT1398/LT1399 ................................................ 12.6V

LT1399HV ....................................................... 15.5V

Input Current (Note 2) ....................................... ±10mA

Output Current................................................. ±100mA

Differential Input Voltage (Note 2) ........................... ±5V

PACKAGE

1

–IN A

2

+IN A

3

*GND

4

*GND

5

*GND

6

*GND

7

+IN B

8

–IN B

16-LEAD PLASTIC SO

T

= 150°C, θJA = 100°C/W

JMAX

*Ground pins are not internally connected. For best channel isolation, connect to ground. Consult factory for Industrial and Military grade parts.

A

/

O

RDER I FOR ATIO

TOP VIEW

A

B

S PACKAGE

16
15
14
13
12
11
10

9

WUW

EN A
OUT A

+

V
GND*
GND*

–

V
OUT B
EN B

U

ARB

G

WU

ORDER PART

NUMBER

LT1398CS

(Note 1)

Output Short-Circuit Duration (Note 3)........ Continuous

Operating Temperature Range ............... – 40°C to 85°C

Specified Temperature Range (Note 4).. –40°C to 85°C

Storage Temperature Range ................ –65°C to 150°C

Junction Temperature (Note 5)............................ 150°C

Lead Temperature (Soldering, 10 sec)................. 300°C

U

TOP VIEW

1

–IN R

2

+IN R

3

*GND

4

–IN G

5

+IN G

6

*GND

7

+IN B

8

–IN B

GN PACKAGE

16-LEAD PLASTIC SSOP

T

= 150°C, θJA = 120°C/W (GN)

JMAX

= 150°C, θJA = 100°C/W (S)

T

JMAX

R

G

B

16
15
14
13
12
11
10

9

S PACKAGE

16-LEAD PLASTIC SO

EN R
OUT R

+

V
EN G
OUT G

–

V
OUT B
EN B

ORDER PART

NUMBER

LT1399CGN
LT1399CS
LT1399HVCS

GN PART MARKING

1399

LECTRICAL C CHARA TERIST

E

(LT1398/LT1399)

ICS

The ● denotes specifications which apply over the specified operating temperature range, otherwise specifications are at TA = 25°C.
For each amplifier: VCM = 0V, V

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

OS

∆VOS/∆T Input Offset Voltage Drift ● 15 µV/°C

+

I

IN

–

I

IN

e

n

+i

n

–i

n

R

IN

C

IN

C

OUT

V

INH

Input Offset Voltage 1.5 10 mV

Noninverting Input Current 10 25 µA

Inverting Input Current 10 50 µA

Input Noise Voltage Density f = 1kHz, RF = 1k, RG = 10Ω, RS = 0Ω 4.5 nV/√Hz
Noninverting Input Noise Current Density f = 1kHz 6 pA/√Hz
Inverting Input Noise Current Density f = 1kHz 25 pA/√Hz
Input Resistance VIN = ±3.5V ● 0.3 1 MΩ
Input Capacitance Amplifier Enabled 2.0 pF

Output Capacitance Amplifier Disabled 8.5 pF
Input Voltage Range, High VS = ±5V ● 3.5 4.0 V

= ±5V, EN = 0V, pulse tested, unless otherwise noted. (Note 4)

S

● 12 mV

● 30 µA

● 60 µA

Amplifier Disabled 2.5 pF

V

= 5V, 0V 4.0 V

S

2

LT1398/LT1399/LT1399HV

LECTRICAL C CHARA TERIST

E

(LT1398/LT1399)

ICS

The ● denotes specifications which apply over the specified operating temperature range, otherwise specifications are at TA = 25°C.
For each amplifier: VCM = 0V, V

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

INL

V

OUTH

V

OUTL

V

OUTH

V

OUTL

CMRR Common Mode Rejection Ratio VCM = ±3.5V ● 42 52 dB
–I

CMRR

PSRR Power Supply Rejection Ratio VS = ±2V to ±5V, EN = V
+I

PSRR

–I

PSRR

A

V

R

OL

I

OUT

I

S

I

EN

SR Slew Rate (Note 6) AV = 10, RL = 150Ω 500 800 V/µs
t

ON

t

OFF

tr, t

f

t

PD

os Small-Signal Overshoot RF = RG = 324Ω, RL = 100Ω, V
t

S

dG Differential Gain (Note 8) RF = RG = 324Ω, RL = 150Ω 0.13 %
dP Differential Phase (Note 8) RF = RG = 324Ω, RL = 150Ω 0.10 DEG

Input Voltage Range, Low VS = ±5V ● –3.5 –4.0 V

Maximum Output Voltage Swing, High VS = ±5V, RL = 100k 3.9 4.2 V

Maximum Output Voltage Swing, Low VS = ±5V, RL = 100k –3.9 – 4.2 V

Maximum Output Voltage Swing, High VS = ±5V, RL = 150Ω 3.4 3.6 V

Maximum Output Voltage Swing, Low VS = ±5V, RL = 150Ω –3.4 –3.6 V

Inverting Input Current VCM = ±3.5V 10 16 µA/V
Common Mode Rejection V

Noninverting Input Current VS = ±2V to ±5V, EN = V
Power Supply Rejection

Inverting Input Current VS = ±2V to ±5V, EN = V
Power Supply Rejection

Large-Signal Voltage Gain V
Transimpedance, ∆V
Maximum Output Current RL = 0Ω ● 80 mA
Supply Current per Amplifier V
Disable Supply Current per Amplifier EN Pin Voltage = 4.5V, RL = 150Ω ● 0.1 100 µA
Enable Pin Current 30 110 µA

Turn-On Delay Time (Note 7) RF = RG = 324Ω, RL = 100Ω 30 75 ns
Turn-Off Delay Time (Note 7) RF = RG = 324Ω, RL = 100Ω 40 100 ns
Small-Signal Rise and Fall Time RF = RG = 324Ω, RL = 100Ω, V
Propagation Delay RF = RG = 324Ω, RL = 100Ω, V

Settling Time 0.1%, AV = –1, RF = RG = 309Ω, RL = 150Ω 25 ns

= ±5V, EN = 0V, pulse tested, unless otherwise noted. (Note 4)

S

VS = 5V, 0V 1.0 V

V

= ±5V, RL = 100k ● 3.7 V

S

VS = 5V, 0V; RL = 100k 4.2 V

VS = ±5V, RL = 100k ● –3.7 V
V

= 5V, 0V; RL = 100k 0.8 V

S

VS = ±5V, RL = 150Ω ● 3.2 V
V

= 5V, 0V; RL = 150Ω 3.6 V

S

VS = ±5V, RL = 150Ω ● –3.2 V
V

= 5V, 0V; RL = 150Ω 0.6 V

S

= ±3.5V ● 22 µA/V

OUT

/∆I

CM

= ±2V, RL = 150Ω 50 65 dB

–

IN

OUT

V

= ±2V, RL = 150Ω 40 100 kΩ

OUT

= 0V ● 4.6 6.5 mA

OUT

–

–

–

= 1V

OUT

P-P

= 1V

OUT

P-P

= 1V

OUT

P-P

● 56 70 dB

12 µA/V

● 3 µA/V

● 27 µA/V

● 200 µA

1.3 ns

2.5 ns
10 %

3

LT1398/LT1399/LT1399HV

LECTRICAL C CHARA TERIST

E

ICS

(LT1399HV)

The ● denotes specifications which apply over the specified operating temperature range, otherwise specifications are at TA = 25°C.
For each amplifier: VCM = 0V, V

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

OS

∆VOS/∆T Input Offset Voltage Drift ● 15 µV/°C

+

I

IN

–

I

IN

e

n

+i

n

–i

n

R

IN

C

IN

C

OUT

V

INH

V

INL

V

OUTH

V

OUTL

V

OUTH

V

OUTL

CMRR Common Mode Rejection Ratio VCM = ±6V ● 42 52 dB
–I

CMRR

PSRR Power Supply Rejection Ratio VS = ±2V to ±7.5V, EN = V
+I

PSRR

–I

PSRR

A

V

R

OL

I

OUT

I

S

I

EN

Input Offset Voltage 1.5 10 mV

Noninverting Input Current 10 25 µA

Inverting Input Current 10 50 µA

Input Noise Voltage Density f = 1kHz, RF = 1k, RG = 10Ω, RS = 0Ω, VS = ±5V 4.5 nV/√Hz
Noninverting Input Noise Current Density f = 1kHz, VS = ±5V 6 pA/√Hz
Inverting Input Noise Current Density f = 1kHz, VS = ±5V 25 pA/√Hz
Input Resistance VIN = ±6V ● 0.3 1 MΩ
Input Capacitance Amplifier Enabled 2.0 pF

Output Capacitance Amplifier Disabled 8.5 pF
Input Voltage Range, High VS = ±7.5V ● 6 6.5 V

Input Voltage Range, Low VS = ±7.5V ● –6 –6.5 V

Maximum Output Voltage Swing, High VS = ±7.5V, RL = 100k 6.4 6.7 V

Maximum Output Voltage Swing, Low VS = ±7.5V, RL = 100k –6.4 –6.7 V

Maximum Output Voltage Swing, High VS = ±7.5V, RL = 150Ω 5.4 5.8 V

Maximum Output Voltage Swing, Low VS = ±7.5V, RL = 150Ω – 5.4 –5.8 V

Inverting Input Current VCM = ±6V 10 16 µA/V
Common Mode Rejection V

Noninverting Input Current VS = ±2V to ±7.5V, EN = V
Power Supply Rejection

Inverting Input Current VS = ±2V to ±7.5V, EN = V
Power Supply Rejection

Large-Signal Voltage Gain V
Transimpedance, ∆V
Maximum Output Current RL = 0Ω ● 80 mA
Supply Current per Amplifier V
Disable Supply Current per Amplifier EN Pin Voltage = 7V, RL = 150Ω ● 0.1 100 µA
Enable Pin Current 30 110 µA

= ±7.5V, EN = 0V, pulse tested, unless otherwise noted. (Note 4)

S

Amplifier Disabled 2.5 pF

= 7.5V, 0V 6.5 V

V

S

VS = 7.5V, 0V 1.0 V

V

= ±7.5V, RL = 100k ● 6.1 V

S

VS = 7.5V, 0V; RL = 100k 6.7 V

VS = ±7.5V, RL = 100k ● –6.1 V
V

= 7.5V, 0V; RL = 100k 0.8 V

S

VS = ±7.5V, RL = 150Ω ● 5.1 V
V

= 7.5V, 0V; RL = 150Ω 5.8 V

S

VS = ±7.5V, RL = 150Ω ● – 5.1 V
V

= 7.5V, 0V; RL = 150Ω 0.6 V

S

= ±6V ● 22 µA/V

OUT

/∆I

CM

= ±4.5V, RL = 150Ω 50 65 dB

–

IN

OUT

V

= ±4.5V, RL = 150Ω 40 100 kΩ

OUT

= 0V ● 4.6 7 mA

OUT

–

–

–

● 12 mV

● 30 µA

● 60 µA

● 56 70 dB

12 µA/V

● 3 µA/V

● 27 µA/V

● 200 µA

4

LT1398/LT1399/LT1399HV

LECTRICAL C CHARA TERIST

E

ICS

(LT1399HV)

The ● denotes specifications which apply over the specified operating temperature range, otherwise specifications are at TA = 25°C.
For each amplifier: VCM = 0V, V

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

SR Slew Rate (Note 6) AV = 10, RL = 150Ω, VS = ±5V 500 800 V/µs
t

ON

t

OFF

tr, t

f

t

PD

os Small-Signal Overshoot RF = RG = 324Ω, RL = 100Ω, V

t

S

dG Differential Gain (Note 8) RF = RG = 324Ω, RL = 150Ω, VS = ±5V 0.13 %
dP Differential Phase (Note 8) RF = RG = 324Ω, RL = 150Ω, VS = ±5V 0.10 DEG

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

Note 2: This parameter is guaranteed to meet specified performance
through design and characterization. It has not been tested.

Note 3: A heat sink may be required depending on the power supply
voltage and how many amplifiers have their outputs short circuited.

Note 4: The LT1398/LT1399/LT1399HV are guaranteed to meet specified
performance from 0°C to 70°C and are designed, characterized and
expected to meet these extended temperature limits, but are not tested at
–40°C and 85°C. Guaranteed I grade parts are available, consult factory.

Note 5: TJ is calculated from the ambient temperature TA and the
power dissipation P

LT1398CS, LT1399CS, LT1399HVCS: T
LT1399CGN: T

Turn-On Delay Time (Note 7) RF = RG = 324Ω, RL = 100Ω, VS = ±5V 30 75 ns
Turn-Off Delay Time (Note 7) RF = RG = 324Ω, RL = 100Ω, VS = ±5V 40 100 ns
Small-Signal Rise and Fall Time RF = RG = 324Ω, RL = 100Ω, V

Propagation Delay RF = RG = 324Ω, RL = 100Ω, V

Settling Time 0.1%, AV = –1V, RF = RG = 309Ω, RL = 150Ω,25ns

according to the following formula:

D

= TA + (PD • 120°C/W)

J

= ±7.5V, EN = 0V, pulse tested, unless otherwise noted. (Note 4)

S

= 1V

, 1.3 ns

P-P

= 1V

, 2.5 ns

P-P

= 1V

,10%

P-P

= 0.5V. This specification is guaranteed by design

IN

V

= ±5V

S

VS = ±5V

V

= ±5V

S

V

= ±5V

S

= TA + (PD • 100°C/W)

J

OUT

OUT

OUT

Note 6: Slew rate is measured at ±2V on a ±3V output signal.
Note 7: Turn-on delay time (tON) is measured from control input to

appearance of 1V at the output, for V
time (t
the output for V
and characterization.

Note 8: Differential gain and phase are measured using a Tektronix
TSG120YC/NTSC signal generator and a Tektronix 1780R Video
Measurement Set. The resolution of this equipment is 0.1% and 0.1°.
Ten identical amplifier stages were cascaded giving an effective
resolution of 0.01% and 0.01°.

) is measured from control input to appearance of 0.5V on

OFF

= 1V. Likewise, turn-off delay

IN

U

W

TYPICAL AC PERFOR A CE

SMALL SIGNAL SMALL SIGNAL SMALL SIGNAL

(V) A

V

S

±5 1 100 365 – 300 150 0.05
±5 2 100 324 324 300 150 0
±5 –1 100 309 309 300 150 0

V

R

(Ω)R

L

F

(Ω)R

(Ω) – 3dB BW (MHz) 0.1dB BW (MHz) PEAKING (dB)

G

5

LT1398/LT1399/LT1399HV

UW

LPER

R

F

O

ATYPICA

CCHARA TERIST

E

C

ICS

Closed-Loop Gain vs Frequency
(AV = 1)

4

2

0

GAIN (dB)

–2

–4

1M 10M 1G100M

= ±5V

V

S

V

= –10dBm

IN

= 365Ω

R

F

= 100Ω

R

L

FREQUENCY (Hz)

Large-Signal Transient Response
(AV = 1)

1398/99 G01

Closed-Loop Gain vs Frequency
(AV = 2)

10

8

6

GAIN (dB)

4

2

1M 10M 1G100M

VS = ±5V
V

= –10dBm

IN

= RG = 324Ω

R

F

= 100Ω

R

L

FREQUENCY (Hz)

Large-Signal Transient Response
(AV = 2)

1398/99 G02

Closed-Loop Gain vs Frequency
(AV = – 1)

4

2

0

GAIN (dB)

–2

–4

1M 10M 1G100M

VS = ±5V

= –10dBm

V

IN

= RG = 309Ω

R

F

R

= 100Ω

L

FREQUENCY (Hz)

Large-Signal Transient Response
(AV = – 1)

1398/99 G03

OUTPUT (1V/DIV)

V

IN

R

= 365Ω

F

= 100Ω

R

L

= ±2.5V

TIME (5ns/DIV)VS = ±5V

2nd and 3rd Harmonic Distortion
vs Frequency

30

TA = 25°C
R

= RG = 324Ω

F

40

= 100Ω

R

L

= ±5V

V

S

50

= 2VPP

V

OUT

60

70

80

DISTORTION (dB)

90

100

110

10

1 100 1000 100000

FREQUENCY (kHz)

HD2

HD3

10000

1398/99 G04

1398/1399 G07

OUTPUT (1V/DIV)

V

= ±1.25V

IN

= RG = 324Ω

R

F

= 100Ω

R

L

TIME (5ns/DIV)VS = ±5V

Maximum Undistorted Output
Voltage vs Frequency

8

7

)

P-P

6

5

4

OUTPUT VOLTAGE (V

TA = 25°C

= 324Ω

R

F

3

= 100Ω

R

L

= ±5V

V

S

2

1

FREQUENCY (MHz)

AV = +1 AV = +2

10 100

1398/99 G05

1398/1399 G08

OUTPUT (1V/DIV)

V

= ±2.5V

IN

= RG = 309Ω

R

F

= 100Ω

R

L

TIME (5ns/DIV)VS = ±5V

PSRR vs Frequency

80

70

60

= RG = 324Ω

F

= 100Ω

L

= +2

V

100k

–PSRR

50

40

PSRR (dB)

30

20

TA = 25°C
R

10

R
A

0

10k 1M 10M 100M

+PSRR

FREQUENCY (Hz)

1398/99 G06

1398/1399 G09

6

LPER

SUPPLY VOLTAGE (±V)

0

0

SUPPLY CURRENT (mA)

1

3

4

5

2

4

59

1398/1399 G15

2

13

6

7

8

6

EN = V

–

EN = 0V

AMBIENT TEMPERATURE (°C)

–50

POSITIVE SUPPLY CURRENT PER AMPLIFIER (mA)

4.75

25

1398/1399 G18

4.00

3.50

–25 0 50

3.25

3.00

5.00

4.50

4.25

3.75

75 100 125

EN = –5V

EN = 0

VS = ±5V

F

O

R

ATYPICA

UW

CCHARA TERIST

E

C

LT1398/LT1399/LT1399HV

ICS

Input Voltage Noise and Current
Noise vs Frequency

1000

100

–IN

+IN

EN

FREQUENCY (Hz)

INPUT NOISE (nV/√Hz OR pA/√Hz)

10

1

10

30 100 300 1k 3k 10k 30k 100k

Maximum Capacitive Load
vs Feedback Resistor

1000

100

1398/1399 G10

Output Impedance vs Frequency

100

RF = RG = 324Ω

= 50Ω

R

L

= +2

A

V

= ±5V

V

S

10

1

0.1

OUTPUT IMPEDANCE (Ω)

0.01
10k

1M 10M100k 100M

FREQUENCY (Hz)

Capacitive Load
vs Output Series Resistor

40

30

RF = RG = 324Ω

= ±5V

V

S

OVERSHOOT < 2%

1398/1399 G11

Output Impedance (Disabled)
vs Frequency

100k

10k

1k

OUTPUT IMPEDANCE (DISABLED) (Ω)

100

100k

1M 10M 100M

FREQUENCY (Hz)

Supply Current vs Supply Voltage

RF = 365Ω

= +1

A

V

= ±5V

V

S

1398/1399 G12

10

CAPACITIVE LOAD (pF)

1

300

5
4
3
2
1

0
–1
–2
–3

OUTPUT VOLTAGE SWING (V)

–4
–5

–50

RF = R
AV = +2
V
PEAKING ≤ 5dB

900 1500 2100 2700 3300

FEEDBACK RESISTANCE (Ω)

Output Voltage Swing
vs Temperature

RL = 150ΩRL = 100k

0

–25

AMBIENT TEMPERATURE (°C)

RL = 150ΩRL = 100k

50

25

= ±5V

S

75

G

1398/1399 G13

100

1398/1399 G16

125

20

10

OUTPUT SERIES RESISTANCE (Ω)

0

10

Enable Pin Current
vs Temperature

–10

VS = ±5V

–20

–30

–40

–50

–60

ENABLE PIN CURRENT (µA)

–70

–80

–50

–25 0

AMBIENT TEMPERATURE (°C)

100 1000

CAPACITIVE LOAD (pF)

EN = 0V

EN = –5V

50 100 125

25 75

1398/1399 G14

Positive Supply Current per
Amplifier vs Temperature

1398/1399 G17

7

LT1398/LT1399/LT1399HV

UW

LPER

F

O

R

ATYPICA

CCHARA TERIST

E

C

ICS

Input Offset Voltage
vs Temperature

3.0
VS = ±5V

2.5

2.0

1.5

1.0

0.5

0

INPUT OFFSET VOLTAGE (mV)

–0.5

–1.0

–25 0 50

–50

25

AMBIENT TEMPERATURE (°C)

75 100 125

All Hostile Crosstalk

0

RF = RG = 324Ω

–10

= 100Ω

R

L

= +2

A

V

–20
–30
–40
–50
–60
–70
–80

ALL HOSTILE CROSSTALK (dB)

–90

–100

R
G
B

100k 10M 100M 500M

1M

FREQUENCY (Hz)

1398/1399 G19

1398/1399 G21

Input Bias Currents
vs Temperature

15

VS = ±5V

12

9

6

3

0

INPUT BIAS CURRENT (µA)

–3

–6

–50

–25 0

+

I

B

–

I

B

50 100 125

25 75

AMBIENT TEMPERATURE (°C)

All Hostile Crosstalk (Disabled)

–10

RF = RG = 324Ω

–20

= 100Ω

R

L

= +2

A

V

–30
–40
–50
–60
–70
–80
–90

ALL HOSTILE CROSSTALK (dB)

–100
–110

R
G
B

100k 10M 100M 500M

1M

FREQUENCY (Hz)

1398/99 G20

1398/1399 G24

8

INPUT

100mV/DIV

Propagation Delay

tPD = 2.5ns

= 100Ω

R

L

= RG = 324Ω

R

F

TIME (500ps/DIV)AV = +2

Rise Time and Overshoot

V

OUT

OUTPUT
200mV/DIV

1398/1399 G22 1398/1399 G23

200mV/DIV

= +2

V

= 100Ω

R

L

= RG = 324Ω

R

F

tr = 1.3ns

TIME (500ps/DIV)A

OS = 10%

UUU

PIN FUNCTIONS

LT1398/LT1399/LT1399HV

LT1398

– IN A (Pin 1): Inverting Input of A Channel Amplifier.
+ IN A (Pin 2): Noninverting Input of A Channel Amplifier.
GND (Pins 3, 4, 5, 6): Ground. Not connected internally.
+ IN B (Pin 7): Noninverting Input of B Channel Amplifier.
– IN B (Pin 8): Inverting Input of B Channel Amplifier.
EN B (Pin 9): B Channel Enable Pin. Logic low to enable.
OUT B (Pin 10): B Channel Output.

V– (Pin 11): Negative Supply Voltage, Usually –5V.
GND (Pins 12, 13): Ground. Not connected internally.

V+ (Pin 14): Positive Supply Voltage, Usually 5V.
OUT A (Pin 15): A Channel Output.
EN A (Pin 16): A Channel Enable Pin. Logic low to enable.

LT1399, LT1399HV

– IN R (Pin 1): Inverting Input of R Channel Amplifier.
+ IN R (Pin 2): Noninverting Input of R Channel Amplifier.
GND (Pin 3): Ground. Not connected internally.
– IN G (Pin 4): Inverting Input of G Channel Amplifier.
+ IN G (Pin 5): Noninverting Input of G Channel Amplifier.
GND (Pin 6): Ground. Not connected internally.
+ IN B (Pin 7): Noninverting Input of B Channel Amplifier.
– IN B (Pin 8): Inverting Input of B Channel Amplifier.
EN B (Pin 9): B Channel Enable Pin. Logic low to enable.
OUT B (Pin 10): B Channel Output.

V– (Pin 11): Negative Supply Voltage, Usually –5V.
OUT G (Pin 12): G Channel Output.
EN G (Pin 13): G Channel Enable Pin. Logic low to enable.

V+ (Pin 14): Positive Supply Voltage, Usually 5V.

U

O

PPLICATI

A

Feedback Resistor Selection

The small-signal bandwidth of the LT1398/LT1399/
LT1399HV is set by the external feedback resistors and the
internal junction capacitors. As a result, the bandwidth is
a function of the supply voltage, the value of the feedback
resistor, the closed-loop gain and the load resistor. The
LT1398/LT1399 have been optimized for ±5V supply
operation and have a – 3dB bandwidth of 300MHz at a gain
of 2. The LT1399HV provides performance similar to the
LT1399. Please refer to the resistor selection guide in the
Typical AC Performance table.

Capacitance on the Inverting Input

Current feedback amplifiers require resistive feedback
from the output to the inverting input for stable operation.

S

I FOR ATIO

WU

U

OUT R (Pin 15): R Channel Output.
EN R (Pin 16): R Channel Enable Pin. Logic low to enable.

Take care to minimize the stray capacitance between the
output and the inverting input. Capacitance on the invert­ing input to ground will cause peaking in the frequency
response (and overshoot in the transient response).

Capacitive Loads

The LT1398/LT1399/LT1399HV can drive many capaci­tive loads directly when the proper value of feedback
resistor is used. The required value for the feedback
resistor will increase as load capacitance increases and as
closed-loop gain decreases. Alternatively, a small resistor
(5Ω to 35Ω) can be put in series with the output to isolate
the capacitive load from the amplifier output. This has the
advantage that the amplifier bandwidth is only reduced
when the capacitive load is present. The disadvantage is
that the gain is a function of the load resistance.

9

LT1398/LT1399/LT1399HV

PPLICATI

A

U

O

S

I FOR ATIO

WU

U

Power Supplies

The LT1398/LT1399 will operate from single or split
supplies from ±2V (4V total) to ±6V (12V total). The
LT1399HV will operate from single or split supplies from
±2V (4V total) to ±7.5V (15V total). It is not necessary to
use equal value split supplies, however the offset voltage
and inverting input bias current will change. The offset
voltage changes about 600µV per volt of supply mis-
match. The inverting bias current will typically change
about 2µA per volt of supply mismatch.

Slew Rate

Unlike a traditional voltage feedback op amp, the slew rate
of a current feedback amplifier is not independent of the
amplifier gain configuration. In a current feedback ampli­fier, both the input stage and the output stage have slew rate
limitations. In the inverting mode, and for gains of 2 or more
in the noninverting mode, the signal amplitude between the
input pins is small and the overall slew rate is that of the
output stage. For gains less than 2 in the noninverting mode,
the overall slew rate is limited by the input stage.

The input slew rate of the LT1398/LT1399/LT1399HV is
approximately 600V/µs and is set by internal currents and
capacitances. The output slew rate is set by the value of the
feedback resistor and internal capacitance. At a gain of 2
with 324Ω feedback and gain resistors and ±5V supplies,
the output slew rate is typically 800V/µs. Larger feedback
resistors will reduce the slew rate as will lower supply
voltages.

Enable/ Disable

will remain enabled at all times, then the EN pin should be
tied to the V– supply. The enable pin current is approxi­mately 30µA when activated. If using CMOS open-drain
logic, an external 1k pull-up resistor is recommended to
ensure that the LT1399 remains disabled in spite of any
CMOS drain-leakage currents.

5.0
TA = 25°C

+

4.5

V

= 5V

= 100Ω

R

L

–

= 0V

V

4

5

6

1398/99 F01

7

OUTPUT

EN

1398/99 F02

4.0

3.5

3.0

2.5

(mA)

S

+I

2.0

1.5

1.0

0.5

0

0

V– = –5V

3

2

1

V+ – VEN (V)

Figure 1. +IS vs (V+ – VEN)

VS = ±5V
V

= 1V

IN

= 324Ω

R

F

R

= 324Ω

G

Figure 2. Amplifier Enable Time, AV = 2

Each amplifier of the LT1398/LT1399/LT1399HV has a
unique high impedance, zero supply current mode which
is controlled by its own EN pin. These amplifiers are
designed to operate with CMOS logic; the amplifiers draw
zero current when these pins are high. To activate each
amplifier, its EN pin is normally pulled to a logic low.
However, supply current will vary as the voltage between
the V+ supply and EN is varied. As seen in Figure 1, +I

S

does vary with (V+ – VEN), particularly when the voltage
difference is less than 3V. For normal operation, it is
important to keep the EN pin at least 3V below the V

+

supply. If a V+ of less than 3V is desired, and the amplifier

10

VS = ±5V

= 1V

V

IN

R

= 324Ω

F

= 324Ω

R

G

R

= 100Ω

L

1398/99 F03

Figure 3. Amplifier Disable Time, AV = 2

OUTPUT

EN

LT1398/LT1399/LT1399HV

PPLICATI

A

U

O

S

I FOR ATIO

WU

U

The enable/disable times are very fast when driven from
standard 5V CMOS logic. Each amplifier enables in about
30ns (50% point to 50% point) while operating on ±5V
supplies (Figure 2). Likewise, the disable time is approxi­mately 40ns (50% point to 50% point) (Figure 3).

Differential Input Signal Swing

To avoid any breakdown condition on the input transis­tors, the differential input swing must be limited to ±5V. In
normal operation, the differential voltage between the
input pins is small, so the ±5V limit is not an issue. In the
disabled mode however, the differential swing can be the
same as the input swing, and there is a risk of device
breakdown if input voltage range has not been properly
considered.

3-Input Video MUX Cable Driver

The application on the first page of this data sheet shows
a low cost, 3-input video MUX cable driver. The scope
photo below (Figure 4) displays the cable output of a
30MHz square wave driving 150Ω. In this circuit the
active amplifier is loaded by the sum of RF and RG of each
disabled amplifier. Resistor values have been chosen to
keep the total back termination at 75Ω while maintaining
a gain of 1 at the 75Ω load. The switching time between
any two channels is approximately 32ns when both
enable pins are driven.

EN A

EN B

OUTPUT

VS = ±5V 20ns/DIV
V

= V

= 2V

INA

INB

at 3.58MHz

Figure 5. 3-Input Video MUX Switching Response (AV = 2)

P-P

1398/99 F05

Using the LT1399 to Drive LCD Displays

Driving the current crop of XGA and UXGA LCD displays
can be a difficult problem because they require drive
voltages of up to 12V, are usually a capacitive load of over
300pF, and require fast settling. The LT1399HV is par­ticularly well suited for driving these LCD displays be­cause it is capable of swinging more than ±6V on ±7.5V
supplies, and it can drive large capacitive loads with a
small series resistor at the output, minimizing settling
time. As seen in Figures 6 and 7, at a gain of +3 with a

16.9Ω output series resistor and a 330pF load, the
LT1399HV is capable of settling to 0.1% in 30ns for a 6V
step. Similarly, a 12V output step settles in 70ns.

When building the board, care was taken to minimize
trace lengths at the inverting input. The ground plane was
also pulled away from RF and RG on both sides of the
board to minimize stray capacitance.

OUTPUT

200mV/DIV

RL = 150Ω

= RG = 324Ω

R

F

f = 10MHz

Figure 4. Square Wave Response

5ns/DIV

1398/99 F04

V

IN

V

OUT

VS = ±5V 20ns/DIV

= 324Ω

R

F

R

= 162Ω

G

= 16.9Ω

R

S

= 330pF

C

L

Figure 6. LT1399/LT1399HV Large-Signal Pulse Response

1398/99 AI06

11

LT1398/LT1399/LT1399HV

PPLICATI

A

V

IN

V

OUT

U

O

S

I FOR ATIO

VS = ±7.5V 50ns/DIV

= 324Ω

R

F

= 162Ω

R

G

R

= 16.9Ω

S

= 330pF

C

L

WU

1398/99 F07

U

Figure 7. LT1399HV Output Voltage Swing

Buffered RGB to Color-Difference Matrix

Two LT1398s can be used to create buffered color­difference signals from RGB inputs (Figure 8). In this
application, the R input arrives via 75Ω coax. It is routed
to the noninverting input of LT1398 amplifier A1 and to
a 1082Ω resistor R8. There is also an 80.6Ω termination

resistor R11, which yields a 75Ω input impedance at the
R input when considered in parallel with R8. R8 connects
to the inverting input of a second LT1398 amplifier (A2),
which also sums the weighted G and B inputs to create a
–0.5 • Y output. LT1398 amplifier B1 then takes the
–0.5 • Y output and amplifies it by a gain of –2, resulting
in the Y output. Amplifier A1 is configured in a noninvert­ing gain of 2 with the bottom of the gain resistor R2 tied
to the Y output. The output of amplifier A1 thus results in
the color-difference output R-Y.

The B input is similar to the R input. It arrives via 75Ω
coax, and is routed to the noninverting input of LT1398
amplifier B2, and to a 2940Ω resistor R10. There is also
a 76.8Ω termination resistor R13, which yields a 75Ω
input impedance when considered in parallel with R10.
R10 also connects to the inverting input of amplifier A2,
adding the B contribution to the Y signal as discussed
above. Amplifier B2 is configured in a noninverting gain
of 2 configuration with the bottom of the gain resistor R4
tied to the Y output. The output of amplifier B2 thus
results in the color-difference output B-Y.

75Ω

SOURCES

R

G

B

+

1/2 LT1398

–

–

1/2 LT1398

+

R11

80.6Ω

R12

86.6Ω

R13

76.8Ω

R8

1082Ω

R9

549Ω

R10

2940Ω

R7

324Ω

–

A2

1/2 LT1398

+

R6

162Ω

–

ALL RESISTORS 1%

= ±5V

V

S

1/2 LT1398

+

Figure 8. Buffered RGB to Color-Difference Matrix

A1

B1

B2

R5

324Ω

R1
324Ω

R2
324Ω

R4
324Ω

R3
324Ω

1398/99 F08

R-Y

Y

B-Y

12

LT1398/LT1399/LT1399HV

PPLICATI

A

U

O

S

I FOR ATIO

WU

U

The G input also arrives via 75Ω coax and adds its
contribution to the Y signal via a 549Ω resistor R9, which
is tied to the inverting input of amplifier A2. There is also
an 86.6Ω termination resistor R12, which yields a 75Ω
termination when considered in parallel with R9. Using
superposition, it is straightforward to determine the
output of amplifier A2. Although inverted, it sums the R,
G and B signals in the standard proportions of 0.3R,

0.59G and 0.11B that are used to create the Y signal.
Amplifier B1 then inverts and amplifies the signal by 2,
resulting in the Y output.

Buffered Color-Difference to RGB Matrix

The LT1399 can be used to create buffered RGB outputs
from color-difference signals (Figure 9). The R output is
a back-terminated 75Ω signal created using resistor R5
and LT1399 amplifier A1 configured for a gain of +2 via
324Ω resistors R3 and R4. The noninverting input of
amplifier A1 is connected via 1k resistors R1 and R2 to
the Y and R-Y inputs respectively, resulting in cancella­tion of the Y signal at the amplifier input. The remaining
R signal is then amplified by A1.

The B output is also a back-terminated 75Ω signal
created using resistor R16 and amplifier A3 configured
for a gain of +2 via 324Ω resistors R14 and R15. The
noninverting input of amplifier A3 is connected via 1k
resistors R12 and R13 to the Y and B-Y inputs respec­tively, resulting in cancellation of the Y signal at the
amplifier input. The remaining B signal is then amplified
by A3.

The G output is the most complicated of the three. It is a
weighted sum of the Y, R-Y and B-Y inputs. The Y input
is attenuated via resistors R6 and R7 such that amplifier
A2’s noninverting input sees 0.83Y. Using superposition,
we can calculate the positive gain of A2 by assuming that
R8 and R9 are grounded. This results in a gain of 2.41 and
a contribution at the output of A2 of 2Y. The R-Y input is
amplified by A2 with the gain set by resistors R8 and R10,
giving an amplification of –1.02. This results in a contri­bution at the output of A2 of 1.02Y – 1.02R. The B-Y input
is amplified by A2 with the gain set by resistors R9 and

R10, giving an amplification of –0.37. This results in a
contribution at the output of A2 of 0.37Y – 0.37B.

If we now sum the three contributions at the output of A2,
we get:

A2

= 3.40Y – 1.02R – 0.37B

OUT

It is important to remember though that Y is a weighted
sum of R, G and B such that:

Y = 0.3R + 0.59G + 0.11B

If we substitute for Y at the output of A2 we then get:

A2

= (1.02R – 1.02R) + 2G + (0.37B – 0.37B)

OUT

= 2G

The back-termination resistor R11 then halves the output
of A2 resulting in the G output.

R1

Y

R-Y

B-Y

ALL RESISTORS 1%

= ±5V

V

S

Figure 9. Buffered Color-Difference to RGB Matrix

1k

R2
1k

R6

205Ω

R8

316Ω

R9

845Ω

R12

1k

R13

1k

R3
324Ω

R4
324Ω

R10
324Ω

R14
324Ω

R15
324Ω

1398/99 F09

R5

75Ω

R11
75Ω

R16
75Ω

R

G

B

+

A1

1/3 LT1399

–

+

R7
1k

A2

1/3 LT1399

–

+

A3

1/3 LT1399

–

13

LT1398/LT1399/LT1399HV

WW

SI PLIFIED SCHE ATIC

, each amplifier

+

V

+IN

EN

–IN

OUT

–

V

1398/99 SS

14

PACKAGE DESCRIPTIO

LT1398/LT1399/LT1399HV

U

Dimensions in inches (millimeters) unless otherwise noted.

GN Package

16-Lead Plastic SSOP (Narrow 0.150)

(LTC DWG # 05-08-1641)

0.189 – 0.196*
(4.801 – 4.978)

16

15

14

12 11 10

13

0.009

(0.229)

9

REF

0.015

± 0.004

(0.38 ± 0.10)

0.007 – 0.0098
(0.178 – 0.249)

0.016 – 0.050

(0.406 – 1.270)

* DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

0° – 8° TYP

× 45°

S Package

16-Lead Plastic Small Outline (Narrow 0.150)

(LTC DWG # 05-08-1610)

0.229 – 0.244

(5.817 – 6.198)

0.053 – 0.068

(1.351 – 1.727)

0.008 – 0.012

(0.203 – 0.305)

16

15

12

0.386 – 0.394*
(9.804 – 10.008)

13

14

0.150 – 0.157**
(3.810 – 3.988)

5

4

3

678

0.004 – 0.0098
(0.102 – 0.249)

0.025

(0.635)

BSC

GN16 (SSOP) 0398

12

11

10

9

0.010 – 0.020

(0.254 – 0.508)

0.008 – 0.010

(0.203 – 0.254)

*

DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

**

DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

× 45°

0° – 8° TYP

0.016 – 0.050

0.406 – 1.270

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen­tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

0.228 – 0.244

(5.791 – 6.197)

0.053 – 0.069

(1.346 – 1.752)

0.014 – 0.019

(0.355 – 0.483)

0.150 – 0.157**
(3.810 – 3.988)

4

5

0.050

(1.270)

TYP

3

2

1

7

6

8

0.004 – 0.010

(0.101 – 0.254)

S16 0695

15

LT1398/LT1399/LT1399HV

U

O

A

PPLICATITYPICAL

Single Supply RGB Video Amplifier

The LT1399 can be used with a single supply voltage of
6V or more to drive ground-referenced RGB video. In
Figure 10, two 1N4148 diodes D1 and D2 have been
placed in series with the output of the LT1399 amplifier
A1 but within the feedback loop formed by resistor R8.
These diodes effectively level-shift A1’s output down­ward by 2 diodes, allowing the circuit output to swing to
ground.

Amplifier A1 is used in a positive gain configuration. The
feedback resistor R8 is 324Ω. The gain resistor is created
from the parallel combination of R6 and R7, giving a
Thevenin equivalent 80.4Ω connected to 3.75V. This
gives an AC gain of +5 from the noninverting input of
amplifier A1 to the cathode of D2. However, the video
input is also attenuated before arriving at A1’s positive

5V

R1
1000Ω

R2
1300Ω

V

IN

R3
160Ω

R4
75Ω

R5

2.32Ω

R6
107Ω

R7
324Ω

input. Assuming a 75Ω source impedance for the signal
driving VIN, the Thevenin equivalent signal arriving at
A1’s positive input is 3V + 0.4VIN, with a source imped­ance of 714Ω. The combination of these two inputs gives
an output at the cathode of D2 of 2 • VIN with no additional
DC offset. The 75Ω back termination resistor R9 halves
the signal again such that V

equals a buffered version

OUT

of VIN.
It is important to note that the 4.7µF capacitor C1 has

been added to provide enough current to maintain the
voltage drop across diodes D1 and D2 when the circuit
output drops low enough that the diodes might otherwise
reverse bias. This means that this circuit works fine for
continuous video input, but will require that C1 charge up
after a period of inactivity at the input.

C1

R8

D1

1N4148

4.7µF

D2

1N4148

1398/99 F10

R9

75Ω

V

OUT

V

S

6V TO 12V

+

A1

1/3 LT1399

–

324Ω

Figure 10. Single Supply RGB Video Amplifier (1 of 3 Channels)

RELATED PARTS

PART NUMBER DESCRIPTION COMMENTS

LT1203/LT1205 150MHz Video Multiplexers 2:1 and Dual 2:1 MUXs with 25ns Switch Time
LT1204 4-Input Video MUX with Current Feedback Amplifier Cascadable Enable 64:1 Multiplexing
LT1227 140MHz Current Feedback Amplifier 1100V/µs Slew Rate, Shutdown Mode
LT1252/LT1253/LT1254 Low Cost Video Amplifiers Single, Dual and Quad Current Feedback Amplifiers
LT1259/LT1260 Dual/Triple Current Feedback Amplifier 130MHz Bandwidth, 0.1dB Flatness > 30MHz
LT1675 Triple 2:1 Buffered Video Mulitplexer 2.5ns Switching Time, 250MHz Bandwidth

13989f LT/TP 0699 4K • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 1998

16

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

●

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