The AD8033/AD8034 FastFET amplifiers are voltage feedback
amplifiers with FET inputs, offering ease of use and excellent
performance. The AD8033 is a single amplifier and the
AD8034 is a dual amplifier. The AD8033/AD8034 FastFET
op amps in ADI’s proprietary XFCB process offer significant
performance improvements over other low cost FET amps, such as
low noise (11 nV/
bandwidth and 80 V/µs slew rate).
With a wide supply voltage range from 5 V to 24 V and fully
operational on a single supply, the AD8033/AD8034 amplifiers
will work in more applications than similarly priced FET
input amps.
outputs for added versatility.
Despite their low cost, the amplifiers provide excellent overall
performance. They offer high common-mode rejection of
–100 dB, low input offset voltage of 2 mV max, and low noise
of 11 nV/
The
quiescent
√
AD8033/AD8034
40 mA of load current.
REV. B
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.
√
Hz and 0.6 fA/√Hz) and high speed (80 MHz
In addition, the
Hz.
AD8033/AD8034
have rail-to-rail
amplifiers only draw 3.3 mA/amplifier of
current while having the capability of delivering up to
Figure 1. Small Signal Frequency Response
The AD8033 is available in small packages: SOIC-8 and SC70.
The AD8034 is also available in small packages: SOIC-8 and
SOT-23-8. They are rated to work over the industrial temperature
range of –40°C to +85°C without a premium over commercial
grade products.
(TA = 25ⴗC, VS = ⴞ5 V, RL = 1 k⍀, Gain = +2, unless otherwise noted.)
ParameterConditionsMinTypMaxUnit
DYNAMIC PERFORMANCE
–3 dB BandwidthG = +1, VO = 0.2 V p-p6580MHz
G = +2, V
G = +2, V
= 0.2 V p-p30MHz
O
= 2 V p-p21MHz
O
Input Overdrive Recovery Time–6 V to +6 V Input135ns
Output Overdrive Recovery Time–3 V to +3 V Input, G = +2135ns
Slew Rate (25% to 75%)G = +2, V
Settling Time to 0.1%G = +2, V
= 4 V Step5580V/µs
O
= 2 V Step95ns
O
G = +2, VO = 8 V Step225ns
NOISE/HARMONIC PERFORMANCE
Distortionf
Second HarmonicR
Third HarmonicR
= 1 MHz, VO = 2 V p-p
C
= 500 Ω–82dBc
L
= 1 kΩ–85dBc
R
L
= 500 Ω–70dBc
L
R
= 1 kΩ–81dBc
L
Crosstalk, Output-to-Outputf = 1 MHz, G = +2–86dB
Input Voltage Noisef = 100 kHz11nV/√Hz
Input Current Noisef = 100 kHz0.7fA/√Hz
DC PERFORMANCE
Input Offset VoltageVCM = 0 V12mV
– T
T
MIN
MAX
Input Offset Voltage Match2.5mV
Input Offset Voltage Drift427µV/
3.5mV
o
C
Input Bias Current1.511pA
T
MIN
– T
MAX
50pA
Open-Loop GainVO = ±3 V8992dB
INPUT CHARACTERISTICS
Common-Mode Input Impedance1000||2.3GΩ||pF
Differential Input Impedance1000||1.7GΩ||pF
Input Common-Mode Voltage Range
FET Input Range–5.0 to +2.2V
Usable Input Range–5.0 to +5.0V
Common-Mode Rejection RatioVCM = (–3 V to +1.5 V)–89–100dB
OUTPUT CHARACTERISTICS
Output Voltage Swing±4.75±4.95V
Output Short Circuit Current40mA
Capacitive Load Drive30% Overshoot, G = +1,35pF
VO = 400 mV p-p
POWER SUPPLY
Operating Range524V
Quiescent Current per Amplifier3.33.5mA
Power Supply Rejection RatioVS = ±2 V–90–100dB
Specifications subject to change without notice.
REV. B–2–
Page 3
AD8033/AD8034
SPECIFICATIONS
(TA = 25ⴗC, VS = 5 V, RL = 1 k⍀, Gain = +2, unless otherwise noted.)
ParameterConditionsMinTypMaxUnit
DYNAMIC PERFORMANCE
–3 dB BandwidthG = +1, VO = 0.2 V p-p7080MHz
G = +2, V
G = +2, V
= 0.2 V p-p32MHz
O
= 2 V p-p21MHz
O
Input Overdrive Recovery Time–3 V to +3 V Input180ns
Output Overdrive Recovery Time–1.5 V to +1.5 V Input, G = +2200ns
Slew Rate (25% to 75%)G = +2, V
= 4 V Step5570V/µs
O
Settling Time to 0.1%G = +2, VO = 2 V Step100ns
NOISE/HARMONIC PERFORMANCE
DistortionfC = 1 MHz, VO = 2 V p-p
Second HarmonicR
Third HarmonicR
= 500 Ω–80dBc
L
= 1 kΩ–84dBc
R
L
= 500 Ω–70dBc
L
= 1 kΩ–80dBc
R
L
Crosstalk, Output to Outputf = 1 MHz, G = +2–86dB
Input Voltage Noisef = 100 kHz11nV/√Hz
Input Current Noisef = 100 kHz0.7fA/√Hz
DC PERFORMANCE
Input Offset VoltageVCM = 0 V12.0mV
– T
T
MIN
MAX
Input Offset Voltage Match2.5mV
Input Offset Voltage Drift430µV/
3.5mV
o
C
Input Bias Current110pA
T
MIN
– T
MAX
50pA
Open-Loop GainVO = 0 V to 3 V8792dB
INPUT CHARACTERISTICS
Common-Mode Input Impedance1000||2.3GΩ||pF
Differential Input Impedance1000||1.7GΩ||pF
Input Common-Mode Voltage Range
FET Input Range0 to 2.0V
Usable Input Range0 to 5.0V
Common-Mode Rejection RatioVCM = 1.0 V to 2.5 V–80–100dB
OUTPUT CHARACTERISTICS
Output Voltage SwingRL = 1 kΩ
0.16 to 4.830.04 to 4.95
V
Output Short Circuit Current30mA
Capacitive Load Drive30% Overshoot, G = +1,25pF
VO = 400 mV p-p
POWER SUPPLY
Operating Range524V
Quiescent Current per Amplifier3.33.5mA
Power Supply Rejection RatioVS = ±1 V–80–100dB
Specifications subject to change without notice.
REV. B
–3–
Page 4
AD8033/AD8034
SPECIFICATIONS
(TA = 25ⴗC, VS = ⴞ12 V, RL = 1 k⍀, Gain = +2, unless otherwise noted.)
ParameterConditionsMinTypMaxUnit
DYNAMIC PERFORMANCE
–3 dB BandwidthG = +1, VO = 0.2 V p-p6580MHz
G = +2, V
G = +2, V
= 0.2 V p-p30MHz
O
= 2 V p-p21MHz
O
Input Overdrive Recovery Time–13 V to +13 V Input100ns
Output Overdrive Recovery Time–6.5 V to +6.5 V Input, G = +2100ns
Slew Rate (25% to 75%)G = +2, V
Settling Time to 0.1%G = +2, V
= 4 V Step5580V/µs
O
= 2 V Step90ns
O
G = +2, VO = 10 V Step225ns
NOISE/HARMONIC PERFORMANCE
Distortionf
Second HarmonicR
Third HarmonicR
= 1 MHz, VO = 2 V p-p
C
= 500 Ω–80dBc
L
= 1 kΩ–82dBc
R
L
= 500 Ω–70dBc
L
= 1 kΩ–82dBc
R
L
Crosstalk, Output to Outputf = 1 MHz, G = +2–86dB
Input Voltage Noisef = 100 kHz11nV/√Hz
Input Current Noisef = 100 kHz0.7fA/√Hz
DC PERFORMANCE
Input Offset VoltageV
= 0 V12.0mV
CM
– T
T
MIN
MAX
3.5mV
Input Offset Voltage Match2.5mV
Input Offset Voltage Drift424µV/
Input Bias Current212pA
– T
T
MIN
MAX
50pA
Open-Loop GainVO = ±8 V8896dB
INPUT CHARACTERISTICS
Common-Mode Input Impedance1000||2.3GΩ||pF
Differential Input Impedance1000||1.7GΩ||pF
Input Common-Mode Voltage Range
FET Input Range–12.0 to +9.0V
Usable Input Range–12.0 to +12.0V
Common-Mode Rejection RatioVCM = ±5 V–92–100dB
OUTPUT CHARACTERISTICS
Output Voltage Swing±11.52± 11.84V
Output Short Circuit Current60mA
Capacitive Load Drive30% Overshoot; G = +135pF
POWER SUPPLY
Operating Range524V
Quiescent Current per Amplifier3.33.5mA
Power Supply Rejection RatioVS = ±2 V–85–100dB
Operating Temperature Range . . . . . . . . . . . –40°C to +85°C
Lead Temperature Range (Soldering 10 sec) . . . . . . . . . 300°C
*Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
REV. B–4–
Page 5
AD8033/AD8034
MAXIMUM POWER DISSIPATION
The maximum safe power dissipation in the AD8033/AD8034
packages is limited by the associated rise in junction temperature
) on the die. The plastic that encapsulates the die will locally
(T
J
reach the junction temperature. At approximately 150°C, which is
the glass transition temperature, the plastic will change its properties. Even temporarily exceeding this temperature limit may change
the stresses that the package exerts on the die, permanently shifting
the parametric performance of the AD8033/AD8034. Exceeding a
junction temperature of 175°C for an extended period of time can
result in changes in silicon devices, potentially causing failure.
The still-air thermal properties of the package and PCB (
ambient temperature (T
package (P
) determine the junction temperature of the die.
D
), and the total power dissipated in the
A
),
JA
The junction temperature can be calculated as follows
TT
=+ ×()Pθ
AD AJJ
The power dissipated in the package (PD) is the sum of the
quiescent power dissipation and the power dissipated in the package
due to the load drive for all outputs. The quiescent power is the
voltage between the supply pins (VS) times the quiescent current (IS).
Assuming the load (R
drive power is VS/2 I
package and some in the load (V
) is referenced to midsupply, then the total
L
some of which is dissipated in the
OUT,
OUT
I
). The difference
OUT
between the total drive power and the load power is the drive
power dissipated in the package:
PQuiescent PowerTotal Drive PowerLoad Power
=+(–)
D
PVI VV R V R
=×
[]
DSS SOUTLOUTL
+
()
[]
×
//–/2
()
2
[]
RMS output voltages should be considered. If RL is referenced
to V
, as in single-supply operation, then the total drive power
S–
I
is V
S
OUT
.
If the rms signal levels are indeterminate, consider the worst
case, when V
= VS/4 for RL to midsupply:
OUT
PVI VR
=×
()
DSS SL
+
//4
()
2
Airflow will increase heat dissipation, effectively reducing
Also, more metal directly in contact with the package leads from
metal traces, through holes, ground, and power planes will reduce
the JA. Care must be taken to minimize parasitic capacitances at
the input leads of high speed op amps as discussed in the Layout,
Grounding, and Bypassing Considerations section.
Figure 2 shows the maximum safe power dissipation in the
package versus the ambient temperature for the SOIC-8 (125°C/W),
SC70
standard 4-layer board.
OUTPUT SHORT CIRCUIT
Shorting the output to ground or drawing excessive current for
the AD8033/AD8034 will likely cause catastrophic failure.
In single-supply operation with RL referenced to VS–, worst case
= VS/2.
is V
OUT
2.0
1.5
SOT-23-8
1.0
SC70-5
0.5
MAXIMUM POWER DISSIPATION – W
0.0
–60–40–20020406080100
SOIC-8
AMBIENT TEMPERATURE – C
Figure 2. Maximum Power Dissipation vs.
Temperature for a Four-Layer Board
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although the
AD8033/AD8034 features proprietary ESD protection circuitry, permanent damage may occur on
devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are
recommended to avoid performance degradation or loss of functionality.
–40ºC to
–40ºC to
–40ºC to
–40ºC to
–40ºC to
–40ºC to
–40ºC to
–40ºC to
–40ºC to
–40ºC to
TPC 1. Small Signal Frequency Response for
Various Gains
1
0
–1
–2
–3
GAIN – dB
–4
–5
G = +1
VO= 200mV p-p
–6
0.1100110
FREQUENCY – MHz
VS= +5V
VS= ⴞ5V
VS= ⴞ12V
TPC 2. Small Signal Frequency Response for
Various Supplies (See Test Circuit 1)
1000
8
G = +2
7
V
= 0.2V p-p
6
5
4
GAIN – dB
3
2
1
0
0.1100110
V
= 1V p-p
OUT
= 4V p-p
V
OUT
V
= 2V p-p
OUT
FREQUENCY – MHz
OUT
TPC 4. Frequency Response for Various Output
Amplitudes (See Test Circuit 2)
8
7
6
5
4
GAIN – dB
3
2
G = +2
1
VO = 200mV p-p
0
0.1100110
FREQUENCY – MHz
VS = ⴞ5V
V
S
VS = +5V
= ⴞ12V
TPC 5. Small Signal Frequency Response for
Various Supplies (See Test Circuit 2)
2
G = +1
1
0
–1
–2
GAIN – dB
–3
–4
–5
–6
0.11001
= 2V p-p
V
OUT
= ⴞ5V
V
S
= +5V
V
S
FREQUENCY – MHz
= ⴞ12V
V
10
S
TPC 3. Large Signal Frequency Response for
Various Supplies (See Test Circuit 1)
7
6
5
4
3
GAIN – dB
2
1
G = +2
VO= 2V p-p
0
0.1100110
VS = ⴞ5V
= +5V
V
S
FREQUENCY – MHz
VS = ⴞ12V
TPC 6. Large Signal Frequency Response for
Various Supplies (See Test Circuit 2)
REV. B–6–
Page 7
AD8033/AD8034
8
C
C
R
L
SNUB
L
= 100pF
= 25⍀
= 100pF
C
= 33pF
L
C
= 2pF
L
VO = 200mV p-p
6
G = +1
4
2
0
GAIN – dB
–2
–4
–6
0.1100110
FREQUENCY – MHz
TPC 7. Small Signal Frequency Response for
Various C
9
8
7
6
5
4
GAIN – dB
3
2
VO = 200mV p-p
R
1
G = +2
0
0.1100110
(See Test Circuit 1)
LOAD
= 3k⍀
F
CF = 0pF
CF = 1.5pF
C
= 2pF
F
FREQUENCY – MHz
CF = 1pF
10
9
8
7
6
5
4
GAIN – dB
3
G = +2
2
VO = 200mV p-p
1
0
0.1100110
C
= 100pF
L
C
= 51pF
L
C
= 33pF
L
C
= 2pF
L
FREQUENCY – MHz
TPC 10. Small Signal Frequency Response for
Various C
8
VO = 200mV p-p
G = +2
7
6
5
4
GAIN – dB
3
2
1
0
0.1100110
(See Test Circuit 2)
LOAD
RL = 500⍀
FREQUENCY – MHz
RL = 1k⍀
TPC 8. Small Signal Frequency Response for
Various RF/CF (See Test Circuit 2)
100
VO = 200mV p-p
10
G = +2
1
IMPEDANCE – ⍀
0.1
0.01
1001k10k100k1M10M100M
FREQUENCY – Hz
TPC 9. Output Impedance vs. Frequency
(See Test Circuits 4 and 7)
REV. B
G = +1
–7–
TPC 11. Small Signal Frequency Response for
Various R
100
80
60
40
GAIN – dB
20
0
–20
10010M1k10k100k1M100M
(See Test Circuit 2)
LOAD
PHASE
FREQUENCY – Hz
VS = ⴞ12V
GAIN
TPC 12. Open-Loop Response
180
150
120
90
PHASE – Degrees
60
30
0
Page 8
AD8033/AD8034
–40
–50
–60
–70
–80
–90
DISTORTION – dBc
–100
–110
–120
G = +2
HD3 RL = 1k⍀
HD2 R
= 1k⍀
L
0.115
FREQUENCY – MHz
HD2 R
HD3 RL = 500⍀
= 500⍀
L
TPC 13. Harmonic Distortion vs. Frequency for
Various Loads (See Test Circuit 2)
–40
G = +2
–50
–60
–70
–80
HD2 VS = 5V
–90
DISTORTION – dBc
–100
–110
–120
0.15
HD2 V
FREQUENCY – MHz
= 24V
S
1
HD3 VS = 5V
HD3 VS = 24V
TPC 14. Harmonic Distortion vs. Frequency for
Various Supply Voltages (See Test Circuit 2)
–40
–50
–60
–70
–80
HD3 G = +2
–90
DISTORTION – dBc
–100
–110
–120
0.151
HD2 G = +1
HD2 G = +2
HD3 G = +1
FREQUENCY – MHz
TPC 16. Harmonic Distortion vs. Frequency for
Various Gains
–20
–30
–40
–50
HD3 VO = 20V p-p
–60
–70
–80
–90
DISTORTION – dBc
–100
–110
–120
0.151
HD3 VO = 10V p-p
HD2 VO = 2V p-p
FREQUENCY – MHz
HD2 VO = 20V p-p
HD2 VO = 10V p-p
HD3 VO = 2V p-p
TPC 17. Harmonic Distortion vs. Frequency for
Various Amplitudes (See Test Circuit 2), VS = 24 V
1000
Hz
100
NOISE – nV/
10
1010M1001k10k100k1M100M
FREQUENCY – Hz
TPC 15. Voltage Noise
80
70
60
VS = +5V
NEGATIVE SIDE
50
40
30
PERCENT OVERSHOOT
20
10
0
1030507090110
VS = ⴞ5V
VS = +5V
POSITIVE SIDE
CAP LOAD – pF
POSITIVE SIDE
VS = ⴞ5V
NEGATIVE SIDE
TPC 18. Capacitive Load vs. Percent Overshoot
G = +1 (See Test Circuit 1)
REV. B–8–
Page 9
AD8033/AD8034
G = +1
25mV/DIV
20ns/DIV
TPC 19. Small Signal Transient Response 5 V
(See Test Circuit 1)
VO = 20V p-p
VO = 8V p-p
VO = 2V p-p
G = +1
38pF
80mV/DIV
15pF
80ns/DIV
TPC 22. Small Signal Transient Response ±5 V
(See Test Circuit 1)
VO = 20V p-p
VO = 8V p-p
VO = 2V p-p
3V/DIV
320ns/DIV
TPC 20. Large Signal Transient Response G = +1
(See Test Circuit 1)
G = –1
1.5V/DIV
V
IN
V
OUT
350ns/DIV
TPC 21. Output Overdrive Recovery (See Test Circuit 3)
3V/DIV
320ns/DIV
TPC 23. Large Signal Transient Response G = +2
(See Test Circuit 2)
G = +1
1.5V/DIV
V
OUT
V
IN
350ns/DIV
TPC 24. Input Overdrive Recovery (See Test Circuit 1)
REV. B
–9–
Page 10
AD8033/AD8034
t
= 0
VIN = 1V
V
OUT
– 2V
VIN = 1V
IN
+0.1%
–0.1%
t
= 0
+0.1%
V
OUT
– 2V
IN
–0.1%
2mV/DIV
1.5s/DIV
TPC 25. Long-Term Settling Time
0
–5
–10
–15
–20
– pA
b
I
–25
–30
–35
–40
208525 30 35 40 45 50 55 60 65 70 75 80
TEMPERATURE – ⴗC
–I
b
+I
b
TPC 26. Ib vs. Temperature
BJT INPUT RANGE
42
36
30
24
= A
18
b
12
6
0
FET INPUT RANGE
10
5
0
–5
–10
– pAI
b
I
–15
–20
–25
–30
–12 –10 –8 –6 –4 –2024681012
+I
b
–I
b
COMMON-MODE VOLTAGE – V
–I
b
+I
b
2mV/DIV
20ns/DIV
TPC 28. 0.1% Short-Term Settling Time
7.0
6.9
6.8
6.7
6.6
6.5
6.4
6.3
6.2
QUIESCENT CURRENT – mA
6.1
6.0
5.9
–40–20
VS = ⴞ12V
VS = ⴞ5V
VS = +5V
020406080
TEMPERATURE – ⴗC
TPC 29. Quiescent Supply Current vs. Tempera-
for Various Supply Voltages
ture
4.0
3.5
3.0
2.5
2.0
1.5
1.0
.50
NORMALIZED OFFSET – mV
0
–.50
–1.0
–1412–12
VS = ⴞ5V
–10 –8 –6 –4 –2 02 4 68 10
COMMON-MODE VOLTAGE – V
VS = +5V
VS = ⴞ12V
14
TPC 27. Input Bias Current vs. Common-Mode
Voltage Range
TPC 30. Input Offset Voltage vs. CommonMode Voltage
REV. B–10–
Page 11
AD8033/AD8034
FREQUENCY – MHz
–40
–70
–100
0.1
CROSSTALK – dB
50
–80
–90
–60
–50
110
SOIC A/B
SOIC B/A
SOT-23 B/A
SOT-23 A/B
–20
–30
–40
–50
CMRR – dB
–60
–70
–80
0.111050
FREQUENCY – MHz
TPC 31. CMRR vs. Frequency (See Test Circuit 7)
1.0
0.8
VCC Ð V
0.6
OH
105
100
95
90
85
80
75
OPEN-LOOP GAIN – dB
70
65
60
–12
RL = 500
⍀
RL = 1k
⍀
OUTPUT VOLTAGE – V
RL = 2k
⍀
12–10 –8 –6 –4 –20246810
TPC 34. Open-Loop Gain vs. Output Voltage for
Various R
LOAD
0.4
VOL Ð V
I
LOAD
EE
– mA
OUTPUT SATURATION – V
0.2
0
0305
10152025
TPC 32. Output Saturation Voltage vs. Load Current
0
–10
–20
–30
–40
–50
PSRR – dB
–60
–70
–80
–90
–100
0.00011000.0010.010.1110
TPC 33. PSRR vs. Frequency (See Test Circuits 6 and 8)
–PSRR
+PSRR
FREQUENCY – MHz
TPC 35. Crosstalk (See Test Circuit 9)
180
150
120
90
FREQUENCY
60
30
0
–1.5–1.0–0.500.51.01.5
VOS – mV
TPC 36. Initial Offset
REV. B
–11–
Page 12
AD8033/AD8034
V
CC
V
EE
1F
+
10nF
AD8033/AD8034
10nF
1F
+
V
SINE
0.2V
p-p
+
–
1k⍀
1k⍀
V
OUT
V
OUT
1.2V/DIV
TPC 37. G = +1 Response VS = ± 5 V
Test Circuits
V
IN
49.9⍀
V
IN
V
CC
1F
+
10nF
R
SNUB
AD8033/AD8034
10nF
+
1F
V
EE
Test Circuit 1. G = +1
976⍀
C
LOAD
1s/DIV
49.9⍀
1.2V/DIV
V
IN
1s/DIV
TPC 38. G = +2 Response VS = ± 5 V
C
F
1k⍀
V
OUT
V
IN
499⍀
49.9⍀
1k⍀
R
F
V
CC
1F
+
10nF
AD8033/AD8034
10nF
+
1F
V
EE
R
SNUB
976⍀
C
LOAD
49.9⍀
V
OUT
Test Circuit 2. G = +2
V
IN
1k⍀
499⍀
1k⍀
V
CC
1F
+
10nF
976⍀
AD8033/AD8034
10nF
+
1F
V
EE
Test Circuit 3. G = –1
49.9⍀
V
CC
1F
+
10nF
V
OUT
AD8033/AD8034
10nF
1F
V
EE
V
SINE
0.2V
+
Test Circuit 4. Output Impedance
G = +1
p-p
+
–
Test Circuit 5. Output Impedance
G = +2
REV. B–12–
Page 13
AD8033/AD8034
V
IN
49.9
1V p-p
+
V
AC
CC
49.9⍀
AD8033/AD8034
10nF
+
1F
V
EE
Test Circuit 6. Positive PSRR
⍀
1k
⍀
⍀
1k
⍀
1k
⍀
1k
V
CC
1F
+
10nF
10nF
1F
V
EE
Test Circuit 7. CMRR
V
–
CC
V
OUT
976
AD8033/AD8034
+
V
CC
1F
+
10nF
V
AD8033/AD8034
1V p-p
–
V
EE
+
V
AC
EE
49.9⍀
OUT
Test Circuit 8. Negative PSRR
1k⍀1k⍀
V
EE
–
TO PORT 1
+
V
⍀
49.9
V
OUT
⍀
IN
–
50⍀
TO PORT 2
1k⍀
499⍀
B
+
V
CC
V
EE
+
A
–
V
CC
1k⍀
499⍀
1k⍀1k⍀
Test Circuit 9. Crosstalk
REV. B
–13–
Page 14
AD8033/AD8034
THEORY OF OPERATION
The incorporation of JFET devices into Analog Devices’ high
voltage XFCB process has given the performance ability to
design the AD8033/AD8034. The AD8033/AD8034 are voltage
feedback rail-to-rail output amplifiers with FET inputs and a
bipolar-enhanced common-mode input range. The use of JFET
devices in high speed amplifiers extends the application
space
into both low input bias current as well as low distortion high
bandwidth areas.
Using N-channel JFETs and a folded cascade input topology, the
common-mode input level operates from 0.2 V below the negative
rail to within 3.0 V of the positive rail. Cascading of the
ensures low input bias current over the entire common-
input stage
mode range
as well as CMRR and PSRR specifications that are above 90 dB.
Additionally, long-term settling issues that normally occur with
high supply voltages are minimized as a result of the cascading.
Output Stage Drive and Capacitive Load Drive
The common emitter output stage adds rail-to-rail output perfor-
and is compensated to drive 35 pF (30% overshoot G = +1).
mance
Additional capacitance can be driven if a small snub resistor is
put in series with the capacitive load, effectively decoupling the
load from the output stage, as shown in TPC 7. The output
can source and sink 20 mA of current within 500 mV of the
stage
rails and 1 mA within 100 mV of the supply rails.
supply
Input Overdrive
An additional feature of the AD8033/AD8034 is a bipolar
input pair that adds rail-to-rail common-mode input performance specifically for applications that cannot tolerate phase
inversion problems.
Under normal common-mode operation, the bipolar input pair
is kept reversed, maintaining Ib at less than 1 pA. When the
common mode comes within 3.0 V of the positive supply
input
rail, I1 turns off and I4 turns on,
+VS
supplying tail current to the
bipolar pair Q25 and Q27. With this configuration, the inputs
can be
inversion (see Figure 3).
As a result of entering the bipolar mode of operation, an offset and
input bias current shift will occur. See TPCs 27 and 30
re-entering the JFET common-mode range, the amplifier will
recover in approximately 100 ns (refer to TPC 24 for input
overload
tection diodes
input bias current.
rails, series input resistance should be included to limit the input
bias current to less than 10 mA.
Input Impedance
The input capacitance of the
with the feedback network, resulting in peaking and ringing
overall response. The equivalent impedance of the feedback
network should be kept small enough to ensure that the parasitic
pole falls well beyond the –3 dB bandwidth of the gain configuration being used. If larger impedance values are desired, the
amplifier can be compensated by placing a small capacitor in
parallel with the feedback resistor. TPC 8 shows the improvement
in frequency response by including a small feedback capacitor
with high feedback resistance values.
Thermal Considerations
Because the AD8034 operates at up to ±12 V supplies in the small
SOT-23-8 package (160°C/W), power dissipation can easily exceed
package limitations, resulting in permanent shifts in device
characteristics and even failure. Likewise, high supply voltages can
cause an increase in junction temperature even with light loads,
resulting in an input bias current and offset drift penalty. The input
bias current will double for every 10°C shown in TPC 26. Refer
to the Maximum Power Dissipation section for an estimation of
die temperature based on load and supply voltage.
driven beyond the positive supply rail without any phase
. After
behavior). Above and below the supply rails, ESD pro-
activate, resulting in an exponentially increasing
If the inputs are to be driven well beyond the
AD8033/AD8034
will form a pole
in the
VTH
–VS
–IN
Q9
R14
Q7
R3
+
V2
–
Q4
Q13
+IN
J2
D5
R7
Q11
Q29
I3
Q1
Q14
VCC
Q28
R8
+
V4
–
V
OUT
R2
Q6
D4
J1
I1I4
Q25
I2
Q27
Figure 3. Simplified AD8033/AD8034 Input Stage
REV. B–14–
Page 15
AD8033/AD8034
LAYOUT, GROUNDING, AND BYPASSING
CONSIDERATIONS
Bypassing
Power supply pins are actually inputs, and care must be taken
so that a noise-free stable dc voltage is applied. The purpose of
bypass capacitors is to create low impedances from the supply to
ground at all frequencies, thereby shunting or filtering a majority
of the noise. Decoupling schemes are designed to minimize the
bypassing impedance at all frequencies with a parallel combination
of capacitors. 0.01 µF or 0.001 µF (X7R or NPO) chip capacitors
are critical and should be placed as close as possible to the
amplifier package. Larger chip capacitors, such as the 0.1 µF
capacitor, can be shared among a few closely spaced active
components in the same signal path. The 10 µF tantalum capacitor
is less critical for high frequency bypassing, and in most cases,
only one per board is needed at the supply inputs.
Grounding
A ground plane layer is important in densely packed PC boards
in
order to spread the current, thereby minimizing parasitic inductances. However,
a circuit is critical
an understanding of where the current flows in
to implementing effective high speed circuit
design. The length of the current path is directly proportional to
the magnitude of
frequency impedance
inductive ground return will
length of the high frequency
the parasitic inductances, and thus the high
of the path. High speed currents in an
create unwanted voltage noise. The
bypass capacitor leads is most critical.
A parasitic inductance in the bypass grounding will work against
the low impedance created by the bypass capacitor. Place the
ground leads of the bypass capacitors at the same physical location.
Because load currents flow from the supplies as well, the ground
for the load impedance should be at the same physical location
as the bypass capacitor grounds. For the larger value capacitors
that are intended to be effective at lower frequencies, the current
return path distance is less critical.
Leakage Currents
Poor PC board layout, contaminants, and the board insulator
material can create leakage currents that are much larger than the
input bias currents of the
between the inputs and nearby runs will set up leakage
AD8033/AD8034
. Any voltage differen
tial
currents
through the PC board insulator, for example, 1 V/100 GΩ = 10 pA.
Similarly, any contaminants on the board can create significant
leakage (skin oils are a common problem).
leakages, put a guard ring (shield) around
To significantly reduce
the inputs and input
leads that are driven to the same voltage potential as the
This way there is no voltage potential between the inputs
surrounding area to set up any leakage currents. For the guard
inputs.
and
ring
to be completely effective, it must be driven by a relatively low
impedance source and should
leads on all sides, above, and below
completely surround the input
using a multilayer board.
Another effect that can cause leakage currents is the charge
absorption of the insulator material itself. Minimizing the amount
of material between the
to reduce the absorption.
®
Teflon
Input Capacitance
or ceramic may be necessary in some instances.
input leads and the guard ring will help
Also, low absorption materials such as
Along with bypassing and ground, high speed amplifiers can be
sensitive to parasitic capacitance between the inputs and ground.
A few pF of capacitance will reduce the input impedance at high
frequencies, in turn increasing the amplifiers’ gain and causing
of the overall response or even oscillations if severe
peaking
enough. It is recommended that the external passive components
that are connected to the input pins be placed as close as possible
to the inputs to avoid parasitic capacitance. The ground and power
planes must be kept at a distance of at least 0.05 mm from the
input pins on all layers of the board.
APPLICATIONS
High Speed Peak Detector
The low input bias current and high bandwidth of the AD8033/
AD8034 make the parts ideal for a fast settling, low leakage peak
detector. The classic fast-low leakage topology with a diode in
the output is limited to 1.4 V p-p max in the case of the
AD8033/AD8034 because of the protection diodes across the
inputs, as depicted in Figure 4.
AD8033/
V
IN
~1.4V p-p MAX
Figure 4. High Speed Peak Detector with Limited Input Range
AD8034
V
OUT
REV. B
–15–
Page 16
AD8033/AD8034
Using the
constructed
AD8033/AD8034
, a unity gain peak detector can be
that will capture a 300 ns pulse while still taking
advantage of the AD8033/AD8034’s low input bias current and
wide common-mode input range, as shown in Figure 5.
Using two amplifiers, the difference between the peak and the
current input level is forced across R2 instead of either amplifier’s
input pins. In the event of a rising pulse, the first amplifier
compensates for the drop across D2 and D3, forcing the voltage
Node 3 equal to Node 1. D1 is off and the voltage drop across
at
R2
is zero. Capacitor C3 speeds up the loop by providing the charge
required by the first amplifier’s input capacitance, helping to
maintain a minimal voltage drop across R2 in the sampling mode.
A negative going edge results in D2 and D3 turning off and D1
turning on, closing the loop around the first amplifier and forcing
– VIN across R2. R4 makes the voltage across D2 zero,
V
OUT
minimizing leakage current and kickback from D3 from affecting
the voltage across C2.
The rate of the incoming edge must be limited so that the output
of the first amplifier does not overshoot the peak value of V
IN
before the second amplifier’s output can provide negative feedback
at the first amplifier’s summing junction. This is accomplished
with the combination of R1 and C1, which allows the voltage at
Node 1 to settle to 0.1% of V
in 270 ns. The selection of C2
IN
and R3 is made by considering droop rate, settling time, and
kickback. R3 prevents overshoot from occurring at Node 3. The
time constants of R1, C1 and R3, C2 are roughly equal to achieve
the best performance. Slower time constants can be selected by
increasing C2 to minimize droop rate and kickback at the cost
of increased settling time. R1 and C1 should also be increased
to match, reducing the incoming pulse’s effect on kickback.
INPUT
OUTPUT
1.00V/DIV 100nS/DIV
Figure 6. Peak Detector Response 4 V 300 ns Pulse
Figure 6 shows the peak detector in Figure 5 capturing a 300 ns
4 V pulse with 10 mV of kickback and a droop rate of 5 V/s. For
larger peak-peak pulses, the time constants of R1, C1 and R3, C3
should be increased to reduce overshoot. The best droop rate will
occur by isolating parasitic resistances from Node 3. This can be
accomplished using a guard band connected to the output of the
second amplifier that surrounds its summing junction (Node 3).
Increasing both time constants by a factor of 3 permits a
larger
peak pulse to be captured and increases the output accuracy.
C3
10pF
R2
1k⍀
LS4148
+V
S
R1
V
IN
49.9⍀
1k⍀
R5
39pF/
C1
120pF
1/2
AD8034
–V
S
D1
D3
LS4148
C4
4.7pF
R4
6k⍀
D2
LS4148
C2
200⍀
R3
AD8034
180pF/560pF
1/2
+V
S
V
OUT
–V
S
Figure 5. High Speed Unity Gain Peak Detector Using AD8034
REV. B–16–
Page 17
INPUT
10k1M10M
FREQUENCY – Hz
–100
REF LEVEL – dB
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
100k
OUTPUT
1.00V/DIV 200nS/DIV
Figure 7. Peak Detector Response 5 V 1 µs Pulse
Figure 7 shows a 5 V peak pulse being captured in 1 s with less
than 1 mV of kickback. With this selection of time constants, up
to a 20 V peak pulse can be captured with no overshoot.
Active Filters
The response of an active filter varies greatly depending on the
performance of the active device. Open-loop bandwidth and gain,
along with the order of the filter, will determine stop-band
attenuation as well as the maximum cutoff frequency, while input
capacitance can set a limit on which passive components are used.
Topologies for active filters are varied, and some are more
dependent on the performance of the active device than others.
The Sallen-Key topology is the least dependent on the active
device, requiring that the bandwidth be flat to beyond the stopband frequency since it is used simply as a gain block. In the
case of high Q filter stages, the peaking must not exceed the
open-loop bandwidth and linear input range of the amplifier.
Using an AD8033/AD8034, a four-pole cascaded Sallen-Key
filter can be constructed with f
C
stop-band attenuation, as shown in Figure 8.
C3
33pF
V
IN
C4
82pF
R4
4.99k⍀
Figure 8. Four-Pole Cascade Sallen-Key Filter
Component values are selected using a normalized cascaded
two-stage Butterworth filter table and Sallen-Key two-pole
active filter equations. The overall frequency response is shown
in Figure 9.
The common-mode input capacitance should be considered
in the component selection.
Filter cutoff frequencies can be increased beyond 1 MHz using
the AD8033/AD8034, but limited open-loop gain and input
impedance begin to interfere with the higher Q stages. This can
cause early roll-off of the overall response.
Additionally, the stop-band attenuation will decrease with
decreasing open-loop gain.
Keeping these limitations in mind, a two-pole Sallen-Key
Butterworth filter with f
has a relatively low Q of 0.707 while still maintaining 15 dB
of attenuation an octave above f
attenuation. The filter and response are shown in Figures 10
and 11, respectively.
R5
49.9⍀
2.49k⍀
V
IN
Figure 10. Two-Pole Butterworth Active Filter
5
0
–5
–10
–15
–20
GAIN – dB
–25
–30
–35
–40
–45
100k100M1M10M
Figure 11. Two-Pole Butterworth Active Filter Response
–17–
= 4 MHz can be constructed that
C
and 35 dB of stop-band
C
22pF
R1
C3
R2
2.49k⍀
C1
10pF
FREQUENCY – Hz
AD8033
+V
S
–V
S
V
OUT
Page 18
AD8033/AD8034
Wideband Photodiode Preamp
Figure 12 shows an I/V converter with an electrical model of a
photodiode.
The basic transfer function is
where I
V
IR
=
OUT
is the output current of the photodiode, and the
PHOTO
×
PHOTOF
sC R
+1
FF
parallel combination of RF and CF sets the signal bandwidth.
The stable bandwidth attainable with this preamp is a function
of R
, the gain bandwidth product of the amplifier, and the total
F
capacitance at the amplifier’s summing junction, including C
S
and the amplifier input capacitance. RF and the total capacitance produce a pole in the amplifier’s loop transmission that can
result in peaking and instability. Adding C
creates a zero in the
F
loop transmission that compensates for the pole’s effect and
reduces the signal bandwidth. It can be shown that the signal
bandwidth resulting in a 45° phase margin (f
) is defined by the
(45)
expression
f
f
()45
2=××π
CR
RC
FS
fCR is the amplifier crossover frequency.
R
is the feedback resistor.
F
C
is the total capacitance at the amplifier summing junction
S
(amplifier + photodiode + board parasitics).
The value of C
that produces f
F
C
=
F
can be shown to be
(45)
C
S
Rf
××2π
FCR
The frequency response in this case will show about 2 dB of
peaking and 15% overshoot. Doubling C
and cutting the
F
bandwidth in half will result in a flat frequency response, with
about 5% transient overshoot.
The preamp’s output noise over frequency is shown in Figure 13.
The pole in the loop transmission translates to a zero in the
amplifier’s noise gain, leading to an amplification of the input
voltage noise over frequency. The loop transmission zero
introduced by C
limits the amplification. The noise gain’s
F
bandwidth extends past the preamp signal bandwidth and
is eventually rolled off by the decreasing loop gain of the
amplifier. Keeping the input terminal impedances matched is
recommended to eliminate common-mode noise peaking
effects that will add to the output noise.
Integrating the square of the output voltage noise spectral density
over frequency and then taking the square root results in the
total rms output noise of the preamp.
C
F
R
F
C
M
C
D
C
M
V
O
I
PHOTO
R
= 1011⍀
SH
C
S
CF + C
V
B
S
R
F
Figure 12. Wideband Photodiode Preamp
f
=
1
2RF (CF + CS + CM + 2CD)
f
=
2
2RFC
f
=
3
(CS + CM + 2CD + CF) /C
RF NOISE
VOLTAGE NOISE – nV/ Hz
f
1
VEN
f
2
NOISE DUE TO AMPLIFIER
1
1
F
f
CR
VEN (CF + CS + CM + 2CD) /C
FREQUENCY – Hz
F
f
3
F
Figure 13. Photodiode Voltage Noise Contributions
REV. B–18–
Page 19
OUTLINE DIMENSIONS
1 3
5 6
2
8
4
7
2.90 BSC
PIN 1
1.60 BSC
1.95
BSC
0.65 BSC
0.38
0.22
0.15 MAX
1.30
1.15
0.90
SEATING
PLANE
1.45 MAX
0.22
0.08
0.60
0.45
0.30
10ⴗ
0ⴗ
2.80 BSC
COMPLIANT TO JEDEC STANDARDS MO-178BA
AD8033/AD8034
8-Lead Standard Small Outline Package [SOIC]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
5.00 (0.1968)
4.80 (0.1890)
4.00 (0.1574)
3.80 (0.1497)
0.25 (0.0098)
0.10 (0.0040)
COPLANARITY
0.10
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
85
1.27 (0.0500)
SEATING
PLANE
COMPLIANT TO JEDEC STANDARDS MS-012AA
BSC
6.20 (0.2440)
5.80 (0.2284)
41
1.75 (0.0688)
1.35 (0.0532)
0.51 (0.0201)
0.33 (0.0130)
0.25 (0.0098)
0.19 (0.0075)
0.50 (0.0196)
0.25 (0.0099)
8ⴗ
0ⴗ
1.27 (0.0500)
0.41 (0.0160)
8-Lead Small Outline Transistor Package [SOT-23]
(RT-8)
Dimensions shown in millimeters
ⴛ 45ⴗ
REV. B
5-Lead Thin Shrink Small Outline Transistor Package [SC70]