Datasheet LT1397, LT1396, LT1395 Datasheet (Linear Technology)

FEATURES

LT1395/LT1396/LT1397

Single/Dual/Quad 400MHz

Current Feedback Amplifier

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DESCRIPTIO

■

400MHz Bandwidth on ±5V (AV = 1)

■

350MHz Bandwidth on ±5V (AV = 2, –1)

■

0.1dB Gain Flatness: 100MHz (AV = 1, 2 and –1)

■

High Slew Rate: 800V/µs

■

Wide Supply Range: ±2V(4V) to ±6V(12V)

■

80mA Output Current

■

Low Supply Current: 4.6mA/Amplifier

■

LT1395: SO-8 Package
LT1396: SO-8 and MSOP Packages
LT1397: SO-14 and SSOP-16 Packages

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APPLICATIO S

■

Cable Drivers

■

Video Amplifiers

■

MUX Amplifiers

■

High Speed Portable Equipment

■

IF Amplifiers

The LT®1395/LT1396/LT1397 are single/dual/quad
400MHz current feedback amplifiers with an 800V/µs slew
rate and the ability to drive up to 80mA of output current.

The LT1395/LT1396/LT1397 operate on all supplies from
a single 4V to ±6V. At ±5V, they draw 4.6mA of supply
current per amplifier.

The LT1395/LT1396/LT1397 are manufactured on Linear
Technology’s proprietary complementary bipolar process.
They have standard single/dual/quad pinouts and they are
optimized for use on supply voltages of ±5V.

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

TYPICAL APPLICATIO

Unity-Gain Video Loop-Through Amplifier Loop-Through Amplifier

–

12.1k

–

LT1396

+

255Ω

1/2

R

F1

BNC INPUTS

R

G1

1.02k

V

IN

0.67pF

HIGH INPUT RESISTANCE DOES NOT LOAD CABLE
EVEN WHEN POWER IS OFF

U

R

63.4Ω

3.01k3.01k

Frequency Response

0

NORMAL SIGNAL

COMMON MODE SIGNAL

100

1k 10k 100k 1G

1M 10M 100M

FREQUENCY (Hz)

1395/6/7 TA02

–

+

LT1396

+

12.1k0.67pF

R

F2

255Ω

1/2

1% RESISTORS
FOR A GAIN OF G:

= G (V

V

OUT

R
RG1 = (G + 3) R

RG2 =
TRIM CMRR WITH R

IN

= R

F1

F2

R

F2

G + 3

+

– V

F2

1395/6/7 TA01

10

–10

V

OUT

–

)

IN

G1

–20

–30

GAIN (dB)

–40

–50

–60

G2

V

IN

1

LT1395/LT1396/LT1397

1
2
3
4

8
7
6
5

TOP VIEW

V

+

OUT B
–IN A
+IN B

OUT A

–IN A
+IN A

V

–

S8 PACKAGE

8-LEAD PLASTIC SO

+

–

+

–

1
2
3
4
5
6
7
8

TOP VIEW

GN PACKAGE

16-LEAD PLASTIC SSOP

16
15
14
13
12
11
10

9

OUT A

–IN A
+IN A

V

+

+IN B
–IN B

OUT B

NC

OUT D
–IN D
+IN D
V

–

+IN C
–IN C
OUT C
NC

+

–

+

–

–

+

–

+

A

W

O

LUTEXI TIS

S

A

WUW

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ARB

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(Note 1)

Total Supply Voltage (V+ to V–) ........................... 12.6V

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

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

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

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

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/

PACKAGE

NC
–IN
+IN

–

V

T

ORDER PART NUMBER

O

RDER I FOR ATIO

TOP VIEW

1
2

–
+

3
4

S8 PACKAGE

8-LEAD PLASTIC SO

= 150°C, θJA = 150°C/W

JMAX

OUT A

8

NC

+

V

7

OUT

6

NC

5

1

–IN A

2

+IN A

3

–

V

4

MS8 PACKAGE

8-LEAD PLASTIC MSOP

T

= 150°C, θJA = 250°C/W

JMAX

ORDER PART NUMBER

Operating Temperature Range (Note 4). –40°C to 85°C
Specified Temperature Range (Note 5).. –40°C to 85°C

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

Junction Temperature (Note 6)............................ 150°C

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

U

TOP VIEW

+

8

V

–
+

7

OUT B

6

–IN A

–
+

5

+IN B

T

= 150°C, θJA = 150°C/W

JMAX

ORDER PART NUMBER

LT1395CS8

S8 PART MARKING

1395

TOP VIEW

1

OUT A

2

–IN A

3

+IN A

+

4

V

5

+IN B

6

–IN B

7

OUT B

14-LEAD PLASTIC SO

T

JMAX

–
+

+
–

S PACKAGE

= 150°C, θJA = 100°C/W

14

OUT D

13

–IN D

–
+

12

+IN D

11

V

10

+IN C

+
–

9

–IN C

8

OUT C

ORDER PART NUMBER

Consult factory for Industrial and Military grade parts.

2

LT1397CS

LT1396CMS8

MS8 PART MARKING

LTDY

–

T

= 150°C, θJA = 135°C/W

JMAX

LT1396CS8

S8 PART MARKING

1396

ORDER PART NUMBER

LT1397CGN

GN PART MARKING

1397

LT1395/LT1396/LT1397

LECTRICAL C CHARA TERIST

E

The ● denotes specifications which apply over the specified operating temperature range, otherwise specifications are at TA = 25°C.
For each amplifier: VCM = 0V, VS = ±5V, pulse tested, unless otherwise noted. (Note 5)

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

V

INH

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 ● 56 70 dB
+I

PSRR

–I

PSRR

A

V

R

OL

I

OUT

I

S

SR Slew Rate (Note 7) AV = –1, RL = 150Ω 500 800 V/µs
–3dB BW –3dB Bandwidth AV = 1, RF = 374Ω, RL = 100Ω 400 MHz

0.1dB BW 0.1dB Bandwidth AV = 1, RF = 374Ω, RL = 100Ω 100 MHz

Input Offset Voltage 1 ±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 2.0 pF
Input Voltage Range, High VS = ±5V ● 3.5 4.0 V

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

Output Voltage Swing, High VS = ±5V 3.9 4.2 V

Output Voltage Swing, Low VS = ±5V –4.2 –3.9 V

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

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

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

Noninverting Input Current VS = ±2V to ±5V 1 2 µA/V
Power Supply Rejection ● 3 µA/V

Inverting Input Current VS = ±2V to ±5V ● 27 µA/V
Power Supply Rejection

Large-Signal Voltage Gain V
Transimpedance, ∆V

OUT

/∆I

–

IN

Maximum Output Current RL = 0Ω ● 80 mA
Supply Current per Amplifier ● 4.6 6.5 mA

ICS

● ±12 mV

● ±30 µA

● ±60 µA

VS = 5V, 0V 4.0 V

V

= 5V, 0V 1.0 V

S

V

= ±5V ● 3.7 V

S

VS = 5V, 0V 4.2 V

V

= ±5V ● –3.7 V

S

VS = 5V, 0V 0.8 V

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

CM

= ±2V, RL = 150Ω 50 65 dB

OUT

V

= ±2V, RL = 150Ω 40 100 kΩ

OUT

A

= 2, RF = RG = 255Ω, RL = 100Ω 300 MHz

V

AV = 2, RF = RG = 255Ω, RL = 100Ω 100 MHz

3

LT1395/LT1396/LT1397

LECTRICAL C CHARA TERIST

E

The ● denotes specifications which apply over the specified operating temperature range, otherwise specifications are at TA = 25°C.
For each amplifier: VCM = 0V, VS = ±5V, pulse tested, unless otherwise noted. (Note 5)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

tr, t

f

t

PD

os Small-Signal Overshoot RF = RG = 255Ω, RL = 100Ω, V
t

S

dG Differential Gain (Note 8) RF = RG = 255Ω, RL = 150Ω 0.02 %
dP Differential Phase (Note 8) RF = RG = 255Ω, RL = 150Ω 0.04 DEG

Small-Signal Rise and Fall Time RF = RG = 255Ω, RL = 100Ω, V
Propagation Delay RF = RG = 255Ω, RL = 100Ω, V

Settling Time 0.1%, AV = –1, RF = RG = 280Ω, RL = 150Ω 25 ns

ICS

OUT
OUT
OUT

= 1V
= 1V
= 1V

P-P
P-P
P-P

1.3 ns

2.5 ns
10 %

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 LT1395C/LT1396C/LT1397C are guaranteed functional over
the operating temperature range of –40°C to 85°C.

Note 5: The LT1395C/LT1396C/LT1397C are guaranteed to meet specified
performance from 0°C to 70°C. The LT1395C/LT1396C/LT1397C are
designed, characterized and expected to meet specified performance from
–40°C and 85°C but is not tested or QA sampled at these temperatures.
For guaranteed I-grade parts, consult the factory.

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Note 6: TJ is calculated from the ambient temperature TA and the
power dissipation P

LT1395CS8: TJ = TA + (PD • 150°C/W)
LT1396CS8: TJ = TA + (PD • 150°C/W)
LT1396CMS8: T
LT1397CS14: TJ = TA + (PD • 100°C/W)
LT1397CGN16: TJ = TA + (PD • 135°C/W)

Note 7: Slew rate is measured at ±2V on a ±3V output signal.
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°.

according to the following formula:

D

= TA + (PD • 250°C/W)

J

TYPICAL AC PERFOR A CE

SMALL SIGNAL SMALL SIGNAL SMALL SIGNAL

V

(V) A

S

±5 1 100 374 – 400 100 0.1
±5 2 100 255 255 350 100 0.1
±5 –1 100 280 280 350 100 0.1

V

RL (Ω)R

(Ω)R

F

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

G

UW

LPER

R

F

O

ATYPICA

CCHARA TERIST

E

C

ICS

Closed-Loop Gain vs Frequency
(AV = 1)

0

–2

–4

GAIN (dB)

–6

1M 10M 1G100M

V

= ±5V

S

= –10dBm

V

IN

R

= 374Ω

F

= 100Ω

R

L

FREQUENCY (Hz)

4

1397 G01

Closed-Loop Gain vs Frequency
(AV = 2)

6

4

2

GAIN (dB)

0

1M 10M 1G100M

VS = ±5V

= –10dBm

V

IN

R

= RG = 255Ω

F

= 100Ω

R

L

FREQUENCY (Hz)

1397 G02

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

0

–2

–4

GAIN (dB)

–6

1M 10M 1G100M

VS = ±5V
V

= –10dBm

IN

= RG = 280Ω

R

F

= 100Ω

R

L

FREQUENCY (Hz)

1397 G03

LPER

LT1395/LT1396/LT1397

UW

R

F

O

ATYPICA

CCHARA TERIST

E

C

ICS

Large-Signal Transient Response
(AV = 1)

OUTPUT (1V/DIV)

V

IN

= 374Ω

R

F

= 100Ω

R

L

= ±2.5V

TIME (10ns/DIV)VS = ±5V

2nd and 3rd Harmonic Distortion
vs Frequency

30

TA = 25°C
R

= RG = 255Ω

F

40

R

= 100Ω

L

V

= ±5V

S

50

V

= 2VPP

OUT

60
70
80

DISTORTION (dB)

90
100
110

1k 100k 1M 100M

10k

FREQUENCY (Hz)

HD3

HD2

10M

1395/6/7 G04

1397 G07

Large-Signal Transient Response
(AV = 2)

OUTPUT (1V/DIV)

V

= ±1.25V

IN

= RG = 255Ω

R

F

= 100Ω

R

L

TIME (10ns/DIV)VS = ±5V

Maximum Undistorted Output
Voltage vs Frequency

8

7

)

P-P

6

5

4

TA = 25°C

OUTPUT VOLTAGE (V

= 374Ω (AV = 1)

R

F

= RG = 255Ω (AV = 2)

R

F

3

= 100Ω

R

L

= ±5V

V

S

2

1M

AV = +1 AV = +2

10M 100M

FREQUENCY (Hz)

1395/6/7 G05

1397 G08

Large-Signal Transient Response
(AV = –1)

OUTPUT (1V/DIV)

= ±5V

V

S

= ±2.5V

V

IN

= RG = 280Ω

R

F

R

= 100Ω

L

TIME (10ns/DIV)

PSRR vs Frequency

80
70
60
50
40

PSRR (dB)

30
20

TA = 25°C
R

10

R
A

0

10k 1M 10M 100M

–PSRR

= RG = 255Ω

F

= 100Ω

L

= +2

V

100k

+PSRR

FREQUENCY (Hz)

1395/6/7 G06

1397 G09

Input Voltage Noise and Current
Noise vs Frequency

1000

100

+i

n

e

n

FREQUENCY (Hz)

INPUT NOISE (nV/√Hz OR pA/√Hz)

10

1

10

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

Maximum Capacitive Load

Output Impedance vs Frequency

100

RF = RG = 255Ω

= 50Ω

R

L

= +2

A

V

= ±5V

V

S

10

OUTPUT IMPEDANCE (Ω)

0.1

0.01

1

10k

1M 10M100k 100M

FREQUENCY (Hz)

1397 G11

–i

n

1397 G10

vs Feedback Resistor

1000

100

10

CAPACITIVE LOAD (pF)

1

300

900 1500 2100 2700 3300

FEEDBACK RESISTANCE (Ω)

RF = R

G

AV = +2

= ±5V

V

S

PEAKING ≤ 5dB

1397 G13

5

LT1395/LT1396/LT1397

AMBIENT TEMPERATURE (°C)

–50

6

9

I

B

+

I

B

–

15

25 75

1397 G19

3

0

–25 0

50 100 125

12

INPUT BIAS CURRENT (µA)

VS = ±5V

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LPER

F

O

R

ATYPICA

E

C

CCHARA TERIST

ICS

Capacitive Load
vs Output Series Resistor

40

30

20

10

OUTPUT SERIES RESISTANCE (Ω)

0

10

CAPACITIVE LOAD (pF)

RF = RG = 255Ω

= ±5V

V

S

OVERSHOOT < 2%

100 1000

Positive Supply Current per
Amplifier vs Temperature

5.00
VS = ±5V

4.95

4.90

4.85

4.80

4.75

4.70

4.65

4.60

4.55

4.50

POSITIVE SUPPLY CURRENT PER AMPLIFIER (mA)

–25 0 50

–50

AMBIENT TEMPERATURE (°C)

25

75 100 125

1397 G14

1397 G17

Supply Current vs Supply Voltage

6

5

4

3

2

SUPPLY CURRENT (mA)

1

0

13

2

0

SUPPLY VOLTAGE (±V)

59

6

4

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

AMBIENT TEMPERATURE (°C)

25

7

8

1397 G15

75 100 125

1397 G18

Output Voltage Swing
vs Temperature

5
4
3
2
1

0
–1
–2
–3

OUTPUT VOLTAGE SWING (V)

–4
–5

–50

–25

VS = ±5V

25

0

AMBIENT TEMPERATURE (°C)

Input Bias Currents
vs Temperature

RL = 150ΩRL = 100k

RL = 150ΩRL = 100k

50

75

100

125

1397 G16

Square Wave Response

OUTPUT (200mV/DIV)

RL = 100Ω

= RG = 255Ω

R

F

f = 10MHz

6

TIME (10ns/DIV)

1395/6/7 G22

Propagation Delay

INPUT (100mV/DIV)

tPD = 2.5ns

= 100Ω

R

L

= RG = 255Ω

R

F

TIME (500ps/DIV)AV = +2

Rise Time and Overshoot

OUTPUT (200mV/DIV)

(200mV/DIV)

OUT

V

1395/6/7 G20 1395/6/7 G21

R
R

= +2

V

= 100Ω

L

= RG = 255Ω

F

tr = 1.3ns

TIME (500ps/DIV)A

OS = 10%

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PIN FUNCTIONS

LT1395/LT1396/LT1397

LT1395CS8
NC (Pin 1): No Connection.
–IN (Pin 2): Inverting Input.
+IN (Pin 3): Noninverting Input.
V– (Pin 4): Negative Supply Voltage, Usually –5V.
NC (Pin 5): No Connection.
OUT (Pin 6): Output.
V+ (Pin 7): Positive Supply Voltage, Usually 5V.
NC (Pin 8): No Connection.

LT1396CMS8, LT1396CS8
OUT A (Pin 1): A Channel Output.
–IN A (Pin 2): Inverting Input of A Channel Amplifier.
+IN A (Pin 3): Noninverting Input of A Channel Amplifier.
V– (Pin 4): Negative Supply Voltage, Usually –5V.
+IN B (Pin 5): Noninverting Input of B Channel Amplifier.

OUT B (Pin 7): B Channel Output.
OUT C (Pin 8): C Channel Output.
–IN C (Pin 9): Inverting Input of C Channel Amplifier.
+IN C (Pin 10): Noninverting Input of C Channel Amplifier.
V– (Pin 11): Negative Supply Voltage, Usually –5V.
+IN D (Pin 12): Noninverting Input of D Channel Amplifier.
–IN D (Pin 13): Inverting Input of D Channel Amplifier.
OUT D (Pin 14): D Channel Output.

LT1397CGN
OUT A (Pin 1): A Channel Output.
–IN A (Pin 2): Inverting Input of A Channel Amplifier.
+IN A (Pin 3): Noninverting Input of A Channel Amplifier.
V+ (Pin 4): Positive Supply Voltage, Usually 5V.
+IN B (Pin 5): Noninverting Input of B Channel Amplifier.

–IN B (Pin 6): Inverting Input of B Channel Amplifier.
–IN B (Pin 6): Inverting Input of B Channel Amplifier.
OUT B (Pin 7): B Channel Output.
V+ (Pin 8): Positive Supply Voltage, Usually 5V.

LT1397CS
OUT A (Pin 1): A Channel Output.
–IN A (Pin 2): Inverting Input of A Channel Amplifier.
+IN A (Pin 3): Noninverting Input of A Channel Amplifier.
V+ (Pin 4): Positive Supply Voltage, Usually 5V.
+IN B (Pin 5): Noninverting Input of B Channel Amplifier.
–IN B (Pin 6): Inverting Input of B Channel Amplifier.

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PPLICATI

A

Feedback Resistor Selection

The small-signal bandwidth of the LT1395/LT1396/LT1397
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

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I FOR ATIO

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OUT B (Pin 7): B Channel Output.

NC (Pin 8): No Connection.

NC (Pin 9): No Connection.

OUT C (Pin 10): C Channel Output.

–IN C (Pin 11): Inverting Input of C Channel Amplifier.

+IN C (Pin 12): Noninverting Input of C Channel Amplifier.

V– (Pin 13): Negative Supply Voltage, Usually –5V.

+IN D (Pin 14): Noninverting Input of D Channel Amplifier.

–IN D (Pin 15): Inverting Input of D Channel Amplifier.

OUT D (Pin 16): D Channel Output.

resistor, the closed-loop gain and the load resistor. The

LT1395/LT1396/LT1397 have been optimized for ±5V

supply operation and have a –3dB bandwidth of 400MHz

at a gain of 1 and 350MHz at a gain of 2. Please refer to the

resistor selection guide in the Typical AC Performance

table.

7

LT1395/LT1396/LT1397

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PPLICATI

A

Capacitance on the Inverting Input

Current feedback amplifiers require resistive feedback
from the output to the inverting input for stable operation.
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 LT1395/LT1396/LT1397 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. See the Typical Perfor­mance Characteristics curves.

Power Supplies

The

LT1395/LT1396/LT1397
split supplies from ±2V (4V total) to ±6V (12V 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 2.5mV per
volt of supply mismatch. The inverting bias current will
typically change about 10µA 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
approximately 600V /µs and is set by internal currents and
capacitances. The output slew rate is set by the value of

S

I FOR ATIO

will operate from single or

LT1395/LT1396/LT1397

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is

the feedback resistor and internal capacitance. At a gain
of 2 with 255Ω 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.

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.

Buffered RGB to Color-Difference Matrix

An LT1397 can be used to create buffered color-differ­ence signals from RGB inputs (Figure 1). In this applica­tion, the R input arrives via 75Ω coax. It is routed to the
noninverting input of LT1397 amplifier A1 and to a 845Ω
resistor R8. There is also an 82.5Ω 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 LT1397 amplifier (A2), which
also sums the weighted G and B inputs to create a
–0.5 • Y output. LT1397 amplifier A3 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 LT1397
amplifier A4, and to a 2320Ω 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 A4 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 A4 thus
results in the color-difference output B-Y.

The G input also arrives via 75Ω coax and adds its
contribution to the Y signal via a 432Ω resistor R9, which
is tied to the inverting input of amplifier A2. There is also
a 90.9Ω termination resistor R12, which yields a 75Ω

8

LT1395/LT1396/LT1397

PPLICATI

A

U

O

S

I FOR ATIO

WU

U

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 A3 then inverts and amplifies the signal by 2,
resulting in the Y output.

R6

127Ω

+

A1

1/4 LT1397

–

R5

255Ω

–

A3

1/4 LT1397

+

–

A4

1/4 LT1397

+

R1
255Ω

R2
255Ω

R4
255Ω

R3
255Ω

1395/6/7 F01

R-Y

Y

B-Y

75Ω

SOURCES
R

G

B

R8

845Ω

R11

82.5Ω
R9

432Ω

R12

90.9Ω

R10

2320Ω

R13

76.8Ω

ALL RESISTORS 1%
V

= ±5V

S

R7

255Ω

–

A2

1/4 LT1397

+

Figure 1. Buffered RGB to Color-Difference Matrix

Buffered Color-Difference to RGB Matrix

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.

An LT1395 combined with an LT1396 can be used to
create buffered RGB outputs from color-difference sig­nals (Figure 2). The R output is a back-terminated 75Ω
signal created using resistor R5 and amplifier A1 config­ured for a gain of +2 via 255Ω 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 255Ω 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

R1

Y

R-Y

B-Y

ALL RESISTORS 1%
V

= ±5V

S

1k
R2

1k

R6

205Ω

R8

261Ω

R9

698Ω

R12

1k

R13

1k

R3
267Ω

R4
267Ω

R10
267Ω

R14
267Ω

R15
267Ω

75Ω

R11

75Ω

R16

75Ω

R5

1395/6/7 F02

+

A1

1/2 LT1396

–

+

R7
1k

A2

LT1395

–

+

A3

1/2 LT1396

–

Figure 2. Buffered Color-Difference to RGB Matrix

R

G

B

9

LT1395/LT1396/LT1397

WW

SI PLIFIED SCHE ATIC

, each amplifier

+

V

+IN

PACKAGE DESCRIPTIO

–IN

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

1395/6/7 SS

9

OUT

–

V

0.009

(0.229)

REF

10

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°

0.229 – 0.244

(5.817 – 6.198)

0.053 – 0.068

(1.351 – 1.727)

0.008 – 0.012

(0.203 – 0.305)

12

0.150 – 0.157**
(3.810 – 3.988)

5

4

3

678

0.0250

(0.635)

BSC

0.004 – 0.0098

(0.102 – 0.249)

GN16 (SSOP) 1098

PACKAGE DESCRIPTIO

(

0.007
(0.18)

0.021

± 0.006

(0.53 ± 0.015)

* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,

PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.

INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006"

° – 6° TYP

0

LT1395/LT1396/LT1397

U

Dimensions in inches (millimeters) unless otherwise noted.

MS8 Package

8-Lead Plastic MSOP

(LTC DWG # 05-08-1660)

0.118 ± 0.004*

0.040

SEATING

PLANE

± 0.006

(1.02 ± 0.15)

0.012
(0.30)

0.0256

REF

(0.65)

BSC

0.152mm) PER SIDE

0.034 ± 0.004

(0.86 ± 0.102)

0.006 ± 0.004
(0.15 ± 0.102)

S8 Package

8-Lead Plastic Small Outline (Narrow 0.150)

(LTC DWG # 05-08-1610)

(3.00 ± 0.102)

0.193 ± 0.006
(4.90 ± 0.15)

8

7

12

6

5

0.118 ± 0.004**

4

3

(3.00 ± 0.102)

MSOP (MS8) 1098

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

0.010 – 0.020

(0.254 – 0.508)

0.008 – 0.010

(0.203 – 0.254)

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

× 45°

0.016 – 0.050

(0.406 – 1.270)

× 45°

0° – 8° TYP

0°– 8° TYP

0.053 – 0.069

(1.346 – 1.752)

0.014 – 0.019

(0.355 – 0.483)

TYP

(1.346 – 1.752)

0.053 – 0.069

0.004 – 0.010

(0.101 – 0.254)

0.228 – 0.244

0.014 – 0.019

(0.355 – 0.483)

TYP

0.050

(1.270)

BSC

(5.791 – 6.197)

S Package

14-Lead Plastic Small Outline (Narrow 0.150)

(LTC DWG # 05-08-1610)

0.004 – 0.010

(0.101 – 0.254)

0.228 – 0.244

0.050

(1.270)

BSC

(5.791 – 6.197)

0.189 – 0.197*
(4.801 – 5.004)

7

8

1

2

0.337 – 0.344*
(8.560 – 8.738)

13

12

14

1

2

11

3

4

5

6

0.150 – 0.157**
(3.810 – 3.988)

3

4

10

9

5

6

8

0.150 – 0.157**
(3.810 – 3.988)

7

SO8 1298

S14 1298

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.

11

LT1395/LT1396/LT1397

U

O

A

PPLICATITYPICAL

Single Supply RGB Video Amplifier

The LT1395 can be used with a single supply voltage of
6V or more to drive ground-referenced RGB video. In
Figure 3, two 1N4148 diodes D1 and D2 have been placed
in series with the output of the LT1395 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 255Ω. The gain resistor is cre­ated from the parallel combination of R6 and R7, giving
a Thevenin equivalent 63.5Ω 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

84.5Ω

R7
255Ω

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
turn off. 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

1395/6/7 TA03

R9

75Ω

V

OUT

6V TO 12V

+

A1

LT1395

–

V

S

255Ω

Figure 3. Single Supply RGB Video Amplifier (1 of 4 Channels)

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139567f LT/TP 0100 4K • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 1999

12

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

●

www.linear-tech.com