Datasheet

ManualsBrandsANALOG DEVICES ManualsLinear ICsLinear IC - Op-amp J-FET PDIP 8

CONNECTION DIAGRAMS

8-Pin Plastic Mini-DIP 8-Pin SOIC

REV. A

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

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

Single Supply, Rail to Rail

Low Power FET-Input Op Amp

AD820

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 617/329-4700 Fax: 617/326-8703

FEATURES

TRUE SINGLE SUPPLY OPERATION

Output Swings Rail to Rail

Input Voltage Range Extends Below Ground

Single Supply Capability from +3 V to +36 V

Dual Supply Capability from 61.5 V to 618 V

EXCELLENT LOAD DRIVE

Capacitive Load Drive Up to 350 pF

Minimum Output Current of 15 mA

EXCELLENT AC PERFORMANCE FOR LOW POWER

800 mA Max Quiescent Current

Unity Gain Bandwidth: 1.8 MHz

Slew Rate of 3.0 V/ms

EXCELLENT DC PERFORMANCE

800 mV Max Input Offset Voltage

1 mV/8C Typ Offset Voltage Drift

25 pA Max Input Bias Current

LOW NOISE

13 nV/√

Hz @ 10 kHz

APPLICATIONS

Battery Powered Precision Instrumentation

Photodiode Preamps

Active Filters

12- to 14-Bit Data Acquisition Systems

Medical Instrumentation

Low Power References and Regulators

PRODUCT DESCRIPTION

The AD820 is a precision, low power FET input op amp that

can operate from a single supply of +3.0 V to 36 V, or dual

supplies of ±1.5 V to ±18 V. It has true single supply capability

with an input voltage range extending below the negative rail,

allowing the AD820 to accommodate input signals below

98765432

INPUT BIAS CURRENT – pA

NUMBER OF UNITS

Input Voltage Noise vs. Frequency

TOP VIEW

(Not to Scale)

AD820

NULL

–IN

+IN

–V

OUT

NULL

TOP VIEW

(Not to Scale)

AD820

–IN

+IN

–V

OUT

ground in the single supply mode. Output voltage swing extends

to within 10 mV of each rail providing the maximum output

dynamic range.

Offset voltage of 800 µV max, offset voltage drift of 1 µV/°C, typ

input bias currents below 25 pA and low input voltage noise

provide dc precision with source impedances up to a Gigaohm.

1.8 MHz unity gain bandwidth, –93 dB THD at 10 kHz and

3 V/µs slew rate are provided for a low supply current of

800 µA. The AD820 drives up to 350 pF of direct capacitive

load and provides a minimum output current of 15 mA. This

allows the amplifier to handle a wide range of load conditions.

This combination of ac and dc performance, plus the outstand-

ing load drive capability, results in an exceptionally versatile am-

plifier for the single supply user.

The AD820 is available in three performance grades. The A and

B grades are rated over the industrial temperature range of

–40°C to +85°C. There is 3 volt grade—the AD820A-3V, rated

over the industrial temperature range.

The AD820 is offered in two varieties of 8-pin package: plastic

DIP, and surface mount (SOIC).

100

1V 20µs1V

Gain of +2 Amplifier; V

= +5, 0, V

= 2.5 V Sine Centered

at 1.25 Volts

Summary of content (16 pages)

PAGE 1
a Single Supply, Rail to Rail Low Power FET-Input Op Amp AD820 FEATURES TRUE SINGLE SUPPLY OPERATION Output Swings Rail to Rail Input Voltage Range Extends Below Ground Single Supply Capability from +3 V to +36 V Dual Supply Capability from 61.5 V to 618 V EXCELLENT LOAD DRIVE Capacitive Load Drive Up to 350 pF Minimum Output Current of 15 mA EXCELLENT AC PERFORMANCE FOR LOW POWER 800 mA Max Quiescent Current Unity Gain Bandwidth: 1.8 MHz Slew Rate of 3.
PAGE 2
AD820–SPECIFICATIONS (V = O, 5 volts (@ T = +258C, V S Parameter DC PERFORMANCE Initial Offset Max Offset over Temperature Offset Drift Input Bias Current at TMAX Input Offset Current at TMAX Open-Loop Gain Conditions VO = 0.2 V to 4 V RL = 100k RL = 10k TMIN to TMAX RL = 1k TMIN to TMAX DYNAMIC PERFORMANCE Unity Gain Frequency Full Power Response Slew Rate Settling Time to 0.1% to 0.
PAGE 3
AD820 (VS = +5 volts (@ TA = +258C, VCM = 0 V, VOUT = 0 V unless otherwise noted) Parameter DC PERFORMANCE Initial Offset Max Offset over Temperature Offset Drift Input Bias Current at TMAX Input Offset Current at TMAX Open-Loop Gain Conditions VO = 4 V to –4 V RL = 100k RL = 10k TMIN to TMAX RL = 1k TMIN to TMAX DYNAMIC PERFORMANCE Unity Gain Frequency Full Power Response Slew Rate Settling Time to 0.1% to 0.
PAGE 4
AD820–SPECIFICATIONS (V = 615 volts (@ T = +258C, V S Parameter DC PERFORMANCE Initial Offset Max Offset over Temperature Offset Drift Input Bias Current at TMAX Input Offset Current at TMAX Open-Loop Gain Conditions VO = +10 V to –10 V RL = 100k RL = 10k TMIN to TMAX RL = 1k TMIN to TMAX DYNAMIC PERFORMANCE Unity Gain Frequency Full Power Response Slew Rate Settling Time to 0.1% to 0.
PAGE 5
AD820 (VS = 0, 3 volts (@ TA = +258C, VCM = 0 V, VOUT = 0.2 V unless otherwise noted) Parameter DC PERFORMANCE Initial Offset Max Offset over Temperature Offset Drift Input Bias Current at TMAX Input Offset Current at TMAX Open-Loop Gain Conditions Min TMIN to TMAX RL = 10k TMIN to TMAX RL = 1k TMIN to TMAX NOISE/HARMONIC PERFORMANCE Input Voltage Noise 0.1 Hz to 10 Hz f = 10 Hz f = 100 Hz f = 1 kHz f = 10 kHz Input Current Noise 0.
PAGE 6
AD820–SPECIFICATIONS NOTES 1 This is a functional specification. Amplifier bandwidth decreases when the input common-mode voltage is driven in the range (+V S –1 V) to +V S. Common-mode error voltage is typically less than 5 mV with the common-mode voltage set at 1 volt below the positive supply. 2 VOL–VEE is defined as the difference between the lowest possible output voltage (V OL) and the minus voltage supply rail (V EE).
PAGE 7
Typical Characteristics–AD820 5 50 VS = 0V, 5V INPUT BIAS CURRENT – pA NUMBER OF UNITS 40 30 20 10 0 –0.5 VS = 0V, +5V AND ±5V VS = ±5V –5 –0.4 –0.3 –0.2 –0.1 0 0.1 0.2 OFFSET VOLTAGE – mV 0.3 0.4 –5 0.5 –4 –3 –2 –1 0 1 2 COMMON-MODE VOLTAGE – V 3 4 5 Figure 4. Input Bias Current vs. Common-Mode Voltage; VS = +5 V, 0 V and VS = ± 5 V Figure 1.
PAGE 8
AD820–Typical Characteristics 10M 40 VS = ±15V 1M INPUT VOLTAGE – µV OPEN-LOOP GAIN –V/V POS RAIL V S = 0V, 5V VS = 0V, 3V 100k RL = 2kΩ 20 RL = 20kΩ NEG RAIL 0 POS RAIL POS RAIL –20 NEG RAIL RL = 100kΩ 10k 100 1k 10k 100k 60 0 LOAD RESISTANCE – Ω 120 180 240 300 OUTPUT VOLTAGE FROM SUPPLY RAILS – mV Figure 7. Open-Loop Gain vs. Load Resistance Figure 10.
PAGE 9
AD820 100 100 80 80 100 60 60 GAIN 40 40 20 20 RL = 2kΩ CL = 100pF 0 0 80 70 100 1k 10k 100k FREQUENCY – Hz 1M 50 30 20 0 10 COMMON-MODE ERROR VOLTAGE – mV OUTPUT IMPEDANCE – Ω 10k 100k 1M 10M 5 ACL = +1 VS = ±15V 1 0.1 0.01 1k 10k 100k FREQUENCY – Hz 1M 4 3 NEGATIVE RAIL POSITIVE RAIL 2 +25 °C +125°C 1 –55 °C +125 °C –55 °C 0 10M –1 0 1 2 3 COMMON-MODE VOLTAGE FROM SUPPLY RAILS –Volts Figure 14. Output Impedance vs. Frequency Figure 17.
PAGE 10
AD820–Typical Characteristics AD820 1000 120 110 ISINK = 10mA 100 ISOURCE = 1mA ISINK = 1mA ISOURCE = 10µA 10 100 POWER SUPPLY REJECTION – dB OUTPUT SATURATION VOLTAGE – mV ISOURCE = 10mA ISINK = 10µA 90 80 70 60 +PSRR –PSRR 50 40 30 20 10 1 –60 0 –40 –20 0 20 40 60 80 100 120 140 10 100 TEMPERATURE – °C 10k 100k FREQUENCY – Hz 1M 10M Figure 22. Power Supply Rejection vs. Frequency Figure 19. Output Saturation Voltage vs.
PAGE 11
AD820 5V 5µs 100 +VS 90 0.01µF 3 VIN 7 AD820 6 2 4 0.01µF RL 100pF VOUT 10 –V S 0% Figure 24. Unity-Gain Follower 5V Figure 27. Large Signal Response Unity Gain Follower; VS = ± 15 V, RL = 10 kΩ 10µs 10mV 100 100 90 90 10 10 0% 0% Figure 25. 20 V, 25 kHz Sine Input; Unity Gain Follower; RL = 600 Ω, VS = ± 15 V 1V Figure 28. Small Signal Response Unity Gain Follower; VS = ± 15 V, RL = 10 kΩ 2µs 1V 100 100 90 90 10 GND REV. A 2µs 10 0% Figure 26.
PAGE 12
AD820 10mV 2µs 100 +VS 90 0.01µF 3 VIN 7 AD820 6 2 RL 4 100pF VOUT 10 GND 0% Figure 33. VS = +5 V, 0 V; Unity Gain Follower Response to 40 mV Step Centered 40 mV Above Ground Figure 30. Unity-Gain Follower 10mV 10k 2µs 100 20k 90 VIN VOUT +VS 0.01µF 3 7 6 AD820 2 RL 4 100pF 10 GND Figure 34. VS = +5 V, 0 V; Gain of Two Inverter Response to 20 mV Step, Centered 20 mV Below Ground Figure 31.
PAGE 13
AD820 In the AD820, n-channel JFETs are used to provide a low offset, low noise, high impedance input stage. Minimum input common-mode voltage extends from 0.2 V below –VS to 1 V less than +VS. Driving the input voltage closer to the positive rail will cause a loss of amplifier bandwidth (as can be seen by comparing the large signal responses shown in Figures 26 and 29) and increased common-mode voltage error as illustrated in Figure 17.
PAGE 14
AD820 Direct capacitive load will interact with the amplifier’s effective output impedance to form an additional pole in the amplifier’s feedback loop, which can cause excessive peaking on the pulse response or loss of stability. Worst case is when the amplifier is used as a unity gain follower. Figure 38 shows the AD820’s pulse response as a unity gain follower driving 350 pF. This amount of overshoot indicates approximately 20 degrees of phase margin—the system is stable, but is nearing the edge.
PAGE 15
AD820 R1 100kΩ +VS +VS A VIN 0.01µF A1 2 4 4 AD820 C 6 A2 2 6 0.01µF 7 3 7 3 Low Power Three-Pole Sallen Key Low-Pass Filter R2 100kΩ AD820 FULL-WAVE RECTIFIED OUTPUT B HALF-WAVE RECTIFIED OUTPUT 2V 2V The AD820’s high input impedance makes it a good selection for active filters. High value resistors can be used to construct low frequency filters with capacitors much less than 1 µF. The AD820’s picoamp level input currents contribute minimal dc errors.
PAGE 16
AD820 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 8 C1792a–10–3/94 Mini-DIP (N) Package 5 0.25 (6.35) PIN 1 1 0.31 (7.87) 4 0.30 (7.62) REF 0.39 (9.91) MAX 0.035±0.01 (0.89±0.25) 0.165±0.01 (4.19±0.25) 0.011±0.003 (0.28±0.08) 0.18±0.03 (4.57±0.76) 0.125 (3.18) MIN 0.018±0.003 (0.46±0.08) 0.10 (2.54) BSC 0.033 (0.84) NOM 15 ° 0° SEATING PLANE SOIC (R) Package 0.150 (3.81) 8 5 0.244 (6.20) 0.228 (5.79) PIN 1 0.157 (3.99) 0.150 (3.81) 1 4 0.197 (5.01) 0.189 (4.80) 0.102 (2.