Texas Instruments OPA1637DGKT

Overview

OPA1637 from Texas Instruments is a fully differential audio operational amplifier with 3.7 nV/√Hz input voltage noise, –120 dB THD+N at 1 kHz, and 9.2 MHz gain-bandwidth product. It operates from ±1.5 V to ±18 V dual supply (or 3–36 V single supply), features power-down mode (<20 µA), and drives high-fidelity ADC inputs in professional audio signal chains.

For engineers reviewing the OPA1637 datasheet, OPA1637 pinout, OPA1637 application, or OPA1637 equivalent, this device is selected for ultra-low-noise differential amplification in high-SNR audio interfaces-especially where bipolar super-beta input performance, wide common-mode range, and low quiescent current (0.95 mA) are critical.

Technical Context

The OPA1637 implements a fully differential amplifier architecture with independent VOCM control, enabling precise alignment of output common-mode voltage to downstream ADC or Class-D amplifier requirements. Its super-beta bipolar input stage delivers 2 nA max input bias current and 400 fA/√Hz current noise at 10 Hz-critical for high-impedance sensor or microphone front-end interfacing.

It supports both differential-input/differential-output and single-ended-input/differential-output configurations. The 15 V/µs differential slew rate, 2.5 MHz full-power bandwidth, and 140 dB CMRR ensure fidelity across dynamic audio signals while maintaining stability into capacitive loads up to 50 pF without isolation resistors.

Key Specifications

Pinout & Package

OPA1637 is housed in an 8-pin VSSOP package (3.00 mm × 3.00 mm body size), optimized for compact audio PCB layouts with thermal performance (RθJA = 181.1°C/W) suitable for surface-mount reflow assembly.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fully differential audio amplifier applications.

Compared with THS4561 and LMH5401, the OPA1637 uniquely balances ultra-low audio-band noise (3.7 nV/√Hz), –120 dB THD+N, VOCM programmability, and sub-1 mA quiescent current-making it the only option qualified for professional-grade ADC front-ends requiring simultaneous low noise, low distortion, and flexible common-mode control.

Availability

OPA1637 is available at Aetrix Electronics and suitable for professional audio mixers, high-resolution ADC interfaces, portable soundbars, and instrument preamplifiers requiring stable component supply and long-term production continuity.

Supply support for OPA1637 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of leadership in precision audio signal conditioning.

The OPA1637 belongs to TI's Burr-Brown™ high-fidelity audio amplifier family, engineered specifically for low-noise, low-distortion differential signal chains in professional and consumer audio equipment where SNR, THD+N, and power efficiency are co-optimized.

FAQ

What is the maximum supply voltage for OPA1637?

The OPA1637 supports dual-supply operation up to ±18 V and single-supply operation up to 36 V. Absolute maximum ratings specify ±20 V for dual supply and 40 V for single supply, but recommended operating conditions limit continuous use to ±18 V to ensure long-term reliability and specified performance across temperature.

Does OPA1637 require external compensation for stability?

The OPA1637 is internally compensated for unity-gain stability with differential loads ≥10 kΩ and capacitive loads ≤50 pF. For heavier capacitive loads or high-gain configurations (>G = 10), external isolation resistors (e.g., 25 Ω) are recommended per Figure 6-27 in the datasheet to maintain phase margin >30°.

How does the VOCM pin function in OPA1637?

The VOCM pin sets the common-mode voltage of the differential output pair (OUT+ and OUT−). When driven with a stable DC voltage (e.g., 2.5 V), it centers the output swing around that level-enabling direct interface to ADCs requiring specific input common-mode ranges without external level-shifting circuitry. VOCM input impedance is 2.5 MΩ || 1 pF.

Can OPA1637 drive a 600-Ω differential load?

Yes-the OPA1637 delivers ±10 V differential output into 600-Ω loads with –107 dB THD+N at 10 kHz (per datasheet Figure 6-3), though output voltage swing is reduced compared to 10-kΩ loads. For sustained 600-Ω operation, ensure junction temperature remains within –40°C to +125°C using appropriate PCB copper area per thermal metrics (RθJB = 102.8°C/W).

What is the power-down behavior of OPA1637?

When the PD pin is pulled low (≤ VS+ – 2.0 V), the OPA1637 enters power-down mode: outputs go high-impedance, quiescent current drops to <20 µA, and turn-off delay is 15 µs. Outputs recover to 90% of final value in 10 µs after PD returns high. Leaving PD floating defaults to normal operation.