Datasheet

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LT1793

Low Noise,

Picoampere Bias Current,

JFET Input Op Amp

1kHz Output Voltage Noise

Density vs Source Resistance

SOURCE RESISTANCE (Ω)

10k

100

100 10k 100k 1M1k

10M

1793 TA02

TOTAL 1kHz VOLTAGE NOISE DENSITY (nV/√Hz)

100M

–

SOURCE

= 25°C

= ±15V

SOURCE

RESISTANCE

ONLY

√

OP AMP

)

+ 4kTR

+ 2qI

The LT

1793 achieves a new standard of excellence in

noise performance for a JFET op amp. For the first time low

voltage noise (6nV/√Hz) is simultaneously offered with

extremely low current noise (0.8fA/√Hz), providing the

lowest total noise for high impedance transducer applica-

tions. Unlike most JFET op amps, the very low input bias

current (3pA typ) is maintained over the entire common

mode range which results in an extremely high input resis-

tance (10

Ω). When combined with a very low input ca-

pacitance (1.5pF) an extremely high input impedance

results, making the LT1793 the first choice for amplifying

low level signals from high impedance transducers. The

low input capacitance also assures high gain linearity when

buffering AC signals from high impedance transducers.

The LT1793 is unconditionally stable for gains of 1 or more,

even with 1000pF capacitive loads. Other key features are

250µV V

and a voltage gain over 4 million. Each indi-

vidual amplifier is 100% tested for voltage noise, slew rate

(3.4V/µs) and gain-bandwidth product (4.2MHz).

Specifications at ±5V supply operation are also provided.

For an even lower voltage noise please see the LT1792 data

sheet.

■

Input Bias Current, Warmed Up: 10pA Max

■

100% Tested Low Voltage Noise: 8nV/√Hz Max

■

A Grade 100% Temperature Tested

■

Offset Voltage Over Temp: 1mV Max

■

Input Resistance: 10

Ω

■

Very Low Input Capacitance: 1.5pF

■

Voltage Gain: 1 Million Min

■

Gain-Bandwidth Product: 4.2MHz Typ

■

Guaranteed Specifications with ±5V Supplies

■

Photocurrent Amplifiers

■

Hydrophone Amplifiers

■

High Sensitivity Piezoelectric Accelerometers

■

Low Voltage and Current Noise Instrumentation

Amplifier Front Ends

■

Two and Three Op Amp Instrumentation Amplifiers

■

Active Filters

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

1793 TA01

2pF

–

LT1097

R2C2 > C1R1

= PARASITIC PHOTODIODE CAPACITANCE

OUT

= 100mV/µWATT FOR 200nm WAVE LENGTH

330mV/µWATT FOR 633nm WAVE LENGTH

10k

1N914

–

1N914

–

LT1793

–

C2 0.022µF

HAMAMATSU

S1336-5BK

(908) 231-0960

OUT

100k

2N3904

Low Noise Light Sensor with DC Servo

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

Summary of content (12 pages)

PAGE 1
LT1793 Low Noise, Picoampere Bias Current, JFET Input Op Amp U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LT®1793 achieves a new standard of excellence in noise performance for a JFET op amp. For the first time low voltage noise (6nV/√Hz) is simultaneously offered with extremely low current noise (0.8fA/√Hz), providing the lowest total noise for high impedance transducer applications.
PAGE 2
LT1793 W W W AXI U U ABSOLUTE RATI GS (Note 1) Supply Voltage ..................................................... ±20V Differential Input Voltage ...................................... ±40V Input Voltage (Equal to Supply Voltage) ............... ±20V Output Short-Circuit Duration ........................ Indefinite Operating Temperature Range ............... – 40°C to 85°C Specified Temperature Range Commercial (Note 8) ......................... – 40°C to 85°C Industrial ..........................
PAGE 3
LT1793 ELECTRICAL CHARACTERISTICS TA = 25°C, VS = ±15V, VCM = 0V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS (Note 2) LT1793AC/LT1793AI MIN TYP MAX LT1793C/LT1793I MIN TYP MAX AVOL Large-Signal Voltage Gain VO = ±12V, RL = 10k VO = ±10V, RL = 1k 1000 500 4500 3500 900 400 4400 3000 V/mV V/mV VOUT Output Voltage Swing RL = 10k RL = 1k ±13.0 ±12.0 ±13.2 ±12.3 ±13.0 ±12.0 ±13.2 ±12.3 V V SR Slew Rate RL ≥ 2k (Note 7) 2.3 3.4 2.3 3.
PAGE 4
LT1793 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the temperature range – 40°C ≤ TA ≤ 85°C. VS = ±15V, VCM = 0V, unless otherwise noted. (Notes 8, 9) LT1793AC/LT1793AI MIN TYP MAX LT1793C/LT1793I MIN TYP MAX VS = ±5V ● ● 0.65 1.00 1.3 1.9 1.6 2.0 4.8 5.5 mV mV (Note 6) ● 5 13 9 50 µV/°C Input Offset Current ● 80 300 100 400 pA IB Input Bias Current ● 700 2400 800 3000 pA VCM Input Voltage Range (Note 5) ● ● 12.6 – 10.0 13.0 – 10.5 12.
PAGE 5
LT1793 U W TYPICAL PERFOR A CE CHARACTERISTICS 1kHz Input Noise Voltage Distribution 0.1Hz to 10Hz Voltage Noise Voltage Noise vs Frequency 100 50 PERCENT OF UNITS (%) VOLTAGE NOISE (1µV/DIV) 40 RMS VOLTAGE NOISE DENSITY (nV/√Hz) TA = 25°C VS = ±15V 510 OP AMPS TESTED 30 20 10 2 4 6 TIME (SEC) 8 1793 G01 V+ VS = ±15V 1 8 7 6 5 4 + V = 5V TO 20V –1.5 –2.0 4.0 3.5 V – = – 5V TO – 20V 3.0 V – +2.
PAGE 6
LT1793 U W TYPICAL PERFOR A CE CHARACTERISTICS Output Voltage Swing vs Load Current Large-Signal Transient Response Small-Signal Transient Response V + –0.8 OUTPUT VOLTAGE SWING (V) 5V/DIV 20mV/DIV AV = 1 CL = 10pF VS = ±15V, ±5V 1793 G10 1µs/DIV AV = 1 CL = 10pF RL = 2k VS = ±15V 1793 G11 5µs/DIV 125°C 25°C –1.0 –1.2 –55°C –1.4 –1.6 VS = ±5V TO ±20V 2.0 1.8 1.6 125°C 1.4 1.2 25°C –55°C V – +1.
PAGE 7
LT1793 U W TYPICAL PERFOR A CE CHARACTERISTICS Short-Circuit Output Current vs Temperature 30 SINK SOURCE 25 20 15 10 – 75 – 50 – 25 0 25 50 75 TEMPERATURE (°C) INPUT BIAS AND OFFSET CURRENTS (A) 35 OUTPUT CURRENT (mA) 30n 5 VS = ±15V SUPPLY CURRENT PER AMPLIFIER (mA) 40 VS = ±15V 4 VS = ± 5V 3 – 75 – 50 – 25 0 25 50 75 TEMPERATURE (°C) 100 125 100 125 1793 G19 W U UO INPUT BIAS CURRENT (pA) 1n BIAS CURRENT 300p 100p 30p OFFSET CURRENT 10p 3p 1p 0.
PAGE 8
LT1793 W U U UO S I FOR ATIO APPLICATI with temperature will occur when the device is nulled with a potentiometer ranging from 10k to 200k. Finer adjustments can be made with resistors in series with the potentiometer (Figure 2b).
PAGE 9
LT1793 W U U UO APPLICATI S I FOR ATIO resulting in a change in voltage dV, which is equal to dQ/CF. The gain therefore is CF/CS. For unity-gain, the CF should equal the transducer capacitance plus the input capacitance of the LT1793 and RF should equal RS. In the noninverting mode example, the transducer current is converted to a change in voltage by the transducer capacitance, CS. This voltage is then buffered by the LT1793 with a gain of 1 + R1/R2.
PAGE 10
LT1793 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.400* (10.160) MAX 8 7 6 5 1 2 3 4 0.255 ± 0.015* (6.477 ± 0.381) 0.300 – 0.325 (7.620 – 8.255) 0.009 – 0.015 (0.229 – 0.381) ( +0.035 0.325 –0.015 8.255 +0.889 –0.381 ) 0.045 – 0.065 (1.143 – 1.651) 0.065 (1.651) TYP 0.100 ± 0.010 (2.540 ± 0.254) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
PAGE 11
LT1793 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 2 3 4 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.
PAGE 12
LT1793 U TYPICAL APPLICATIONS N 10Hz Fourth Order Chebyshev Lowpass Filter (0.01dB Ripple) R2 237k R1 237k VIN C2 100nF R3 249k R5 154k 15V 2 3 – + C1 33nF 7 6 LT1793 R4 154k R6 249k C4 330nF 4 2 – 3 + C3 10nF LT1793 6 VOUT 1793 TA04 –15V TYPICAL OFFSET ≈ 0.8mV 1% TOLERANCES FOR VIN = 10VP-P, VOUT = –121dB AT f > 330Hz = – 6dB AT f = 16.