OP27G Overview

The OP27 is a high-performance precision operational amplifier that successfully blends low offset and drift characteristics with low noise and high speed. It has an exceptionally low offset voltage down to 25 µV, a maximum drift of 0.6 µV/℃, and a high gain of 1.8 million. Its dynamic capabilities are supported by an 8 MHz gain bandwidth product and a 2.8 V/µs slew rate. Additionally, an integrated bias current cancellation circuit successfully minimizes input bias current, maintaining a low 10nA under standard conditions.

Beyond its input precision, the OP27 features an output stage with robust load-driving capabilities. It delivers a guaranteed 10V swing into a 600Ω load with low distortion, while boasting exceptional PSRR and CMRR ratings that both exceed 120 dB. Long-term drift is maintained at a minimal 0.2 µV per month, allowing designers to reach discrete-level performance in a single chip.

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OP27G Principle

The OP27G operates on a bipolar transistor architecture combined with an internal bias current cancellation circuit, enabling extremely low noise and very low input offset voltage. Its input stage uses on-chip Zener zap-trimming technology to precisely calibrate offset voltage during manufacturing, while bias current cancellation keeps input bias current at the nanoampere (nA) level, minimizing errors caused by source impedance.

The device also features a low 1/f noise corner frequency of just 2.7 Hz and a high open-loop gain of up to 1.8 million. Combined with over 120 dB of CMRR and PSRR, it delivers excellent signal fidelity and noise immunity when amplifying low-level signals. In addition, its push-pull output stage provides strong load-driving capability while maintaining low distortion and high dynamic accuracy across a wide frequency range.

OP27G Specifications

Analog Devices Inc. OP27GS key technical specifications, performance, parameters are listed below.

OP27G Pinout

Pin 1 (VOS TRIM): Used to connect an external potentiometer for precise tuning and cancellation of the input offset voltage.

Pin 2 (-IN): Inverting input pin, where an input signal results in an output signal of the opposite phase.

Pin 3 (+IN): Non-inverting input pin, where an input signal results in an output signal of the same phase.

Pin 4 (V-): Negative power supply pin, connected to the negative voltage rail or ground.

Pin 5 (NC): No Connection pin, which is not internally connected to any circuitry and should be left floating.

Pin 6 (OUT): Signal output pin, delivering the amplified and processed high-precision voltage signal.

Pin 7 (V+): Positive power supply pin, connected to the positive voltage rail.

Pin 8 (VOS TRIM): The second offset trim pin, used in conjunction with Pin 1 to balance the offset voltage.

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OP27G Features

l  Low noise: 80 nV p-p (0.1 Hz to 10 Hz), 3 nV/√Hz

l  Low drift: 0.2 µV/°C

l  High speed: 2.8 V/µs slew rate, 8 MHz gain bandwidth

l  Low VOS: 10 µV

l  CMRR: 126 dB at VCM of ±11 V

l  High open-loop gain: 1.8 million

l  Available in die form

OP27G Applications

1. Precision Instrumentation and Measurement Systems

OP27G features extremely low offset voltage, low temperature drift, and high open-loop gain, making it ideal for precision instrumentation. It is widely used in digital multimeters, data loggers, laboratory test equipment, and sensor measurement systems.

2. Sensor Signal Conditioning

Many sensors, such as pressure sensors, strain gauges, thermocouples, and load cells, generate very low-level output signals that are susceptible to noise. The OP27G's low-noise architecture and high common-mode rejection ratio (CMRR) enable accurate signal amplification while minimizing interference.

3. Data Acquisition (DAQ) Systems

In high-resolution data acquisition systems, the analog front end must preserve signal integrity before analog-to-digital conversion. With its 8 MHz gain-bandwidth product, low noise performance, and excellent dynamic accuracy, the OP27G is well suited for DAQ modules, industrial monitoring equipment, and scientific instrumentation.

4. Precision Voltage Comparators and Threshold Detection Circuits

The OP27G can be used in precision voltage detection and comparison circuits where accurate switching thresholds are critical. Typical applications include over-voltage protection, under-voltage monitoring, battery management systems, power supply supervision, and industrial control systems that require voltage monitoring.

5. Professional Audio and Microphone Preamplifiers

Thanks to its ultra-low noise density and low distortion characteristics, the OP27G is widely used in professional audio equipment, including microphone preamplifiers, audio mixers, recording consoles, tape-head amplifiers, and high-fidelity sound systems. Its excellent signal-to-noise ratio helps preserve audio quality during amplification.

6. Precision Summing, Integrator, and Analog Computing Circuits

The OP27G is commonly employed in precision summing amplifiers, active filters, integrators, and analog computing circuits. Its low offset drift and long-term stability ensure accurate mathematical operations over extended periods, making it suitable for industrial automation, process control, and scientific research applications.

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OP27G Functional Block Diagram

Input Stage:

Uses bipolar differential pairs (Q1A/Q1B, Q2A/Q2B) with Q6 bias current cancellation to minimize input bias current and noise. Offset is trimmed via R11 and R21 (VOS ADJ pins), with additional precision tuning using on-chip Zener-zap laser trimming.

Intermediate Stage:

Based on Q23/Q24 differential amplification with current sources and multi-capacitor frequency compensation (C1–C4). Ensures high stability, 1.8M open-loop gain, 8 MHz bandwidth, and 2.8 V/μs slew rate.

Output Stage:

Push-pull output using Q45/Q46 provides strong drive capability, supporting ±10 V swing into 600 Ω with low distortion and high linearity.

OP27 Op-amp Series

OP27G Package

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