Texas Instruments OPA860ID

Overview

OPA860ID from Texas Instruments is a monolithic operational transconductance amplifier (OTA) with integrated closed-loop unity-gain buffer, designed for wide-bandwidth signal conditioning in high-speed video, RF/IF, and precision timing systems. It delivers 80MHz open-loop OTA bandwidth (G = +5), 900V/µs slew rate, 95mA/V transconductance, and 1600MHz buffer bandwidth with 4000V/µs slew rate - enabling ns-pulse integration, AGC amplifiers, and wideband LED drivers.

For engineers reviewing the OPA860ID datasheet, OPA860ID pinout, OPA860ID application, or OPA860ID equivalent, key selection considerations include its dual-section architecture (independent OTA and buffer biasing), external IQ-adjust resistor control (RADJ), ±5V operation, SO-8 thermal performance (θJA = 125°C/W), and differential gain/phase specs for broadcast video compliance.

Technical Context

The OPA860ID integrates two functionally isolated analog sections: a bipolar OTA with B/E/C terminals modeled after a voltage-controlled current source (gm = 95–160mA/V, adjustable via RADJ), and a separate high-speed buffer with 1600MHz bandwidth and 4000V/µs slew rate. The OTA's transconductance remains stable over temperature due to IQ-tracking design, while the buffer's PSRR (–PSRR = 45–54dB) and low input offset drift (±125µV/°C) support precision DC-coupled paths.

Both sections operate from ±2.5V to ±6.5V supplies but share no internal bias circuitry - enabling independent optimization of OTA bandwidth (via RADJ) and buffer linearity (via load impedance). The OTA's E-input resistance (6.3–13.3Ω) and C-output impedance (54kΩ||2pF) define its current-source behavior, while the buffer's 1.4Ω closed-loop output impedance ensures drive capability into 50Ω loads.

Key Specifications

Pinout & Package

OPA860ID is housed in an SO-8 surface-mount package (D suffix) with exposed pad thermal enhancement. Pin 1 is IQ Adjust (RADJ connection), pins 2–3 are B/E inputs, pin 4 is V−, pin 5 is C output, pin 6 is Out (buffer output), pin 7 is In (buffer input), and pin 8 is V+.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar transconductance amplifier and high-speed buffer applications.

Compared with OPA695IDBVR and LMH6723MA/NOPB, the OPA860ID uniquely combines independently configurable OTA and buffer sections - enabling system-level trade-offs between transconductance linearity, bandwidth, and power that single-amplifier alternatives cannot match.

Availability

OPA860ID is available at Aetrix Electronics and suitable for video/broadcast equipment, high-speed data acquisition, and wideband LED driver applications requiring stable component supply across industrial temperature ranges (–45°C to +85°C).

Supply support for OPA860ID 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 expertise in high-speed amplifier design and precision signal chain solutions.

The OPA860ID belongs to TI's OPA high-speed amplifier family, engineered specifically for wideband transconductance and buffer functions in demanding video, communications, and instrumentation systems where both current-source programmability and GHz-range voltage gain are required.

FAQ

What is the primary functional distinction between the OTA and buffer sections in the OPA860ID?

The OPA860ID integrates two electrically isolated analog sections: the OTA (pins 1–5) functions as a voltage-controlled current source with B/E/C terminals and externally adjustable transconductance (via RADJ), while the buffer (pins 6–8) is a fixed unity-gain voltage amplifier with 1600MHz bandwidth and 4000V/µs slew rate. Their bias circuits are independent - changing RADJ affects only the OTA's gm and bandwidth, not the buffer's linearity or settling time. This separation allows concurrent optimization of current-mode signal processing and high-fidelity voltage output driving in a single SO-8 package.

Can the OPA860ID be used as a drop-in replacement for the OPA660 in existing designs?

The OPA860ID is explicitly positioned as an OPA660 upgrade per its datasheet, offering higher bandwidth (80MHz vs. 40MHz OTA), faster slew rate (900V/µs vs. 500V/µs), and added buffer functionality. However, it is not pin-compatible: OPA660 uses SO-8 but assigns different functions to pins (e.g., OPA660 pin 1 is NC, while OPA860ID pin 1 is IQ Adjust). Layout changes are required to route RADJ and separate OTA/buffer I/O. The OPA860ID also draws higher quiescent current (11.2mA vs. 6.5mA), necessitating thermal reassessment. Thus, it is a functional upgrade requiring schematic and PCB revision - not a drop-in replacement.

What is the recommended RADJ resistor value for achieving 11.2mA quiescent current in the OPA860ID at +25°C?

The OPA860ID datasheet specifies that a 250Ω resistor connected from pin 1 (IQ Adjust) to V− sets the nominal quiescent current to 11.2mA at +25°C. This value is confirmed in the Electrical Characteristics table under "Maximum Quiescent Current" and "Minimum Quiescent Current" rows with RADJ = 250Ω. The resistor must be placed close to the device with short traces to minimize noise coupling; deviation beyond ±1% tolerance may shift gm by >3%, affecting bandwidth flatness. For production designs, 1% metal-film resistors are recommended, and temperature drift of RADJ should be considered - a 100ppm/°C part introduces <0.5% IQ change over –40°C to +85°C.

How does the OPA860ID's differential gain and phase performance impact its suitability for broadcast video applications?

The OPA860ID delivers 0.06% differential gain error and 0.02° differential phase error (typical, NTSC/PAL), meeting SMPTE RP 168 and ITU-R BT.601 broadcast video standards for luminance/chrominance signal integrity. These values are measured under standard 500Ω load conditions with 200mVPP output, confirming minimal color distortion during composite video amplification. Unlike general-purpose op-amps with >0.5% gain error, the OPA860ID's trimmed architecture maintains consistent AC coupling response across 0–5MHz, eliminating need for external peaking networks or post-processing correction - directly enabling reliable use in professional video line drivers, switchers, and distribution amplifiers without additional calibration.

Does the OPA860ID support single-supply operation, and what are the limitations?

The OPA860ID is specified for dual-supply operation (±2.5V to ±6.5V) and does not support true single-supply use. Its B-input common-mode range extends to ±VS, but E- and C-terminal voltage compliance (±4.2V and ±4.7V respectively) and output swing (±4.0V into 500Ω) require symmetric rails for full dynamic range. Attempting single-supply operation (e.g., 0V/10V) forces the OTA's E-node near ground, violating its ±4.2V compliance and causing clipping or instability. While DC-biased configurations using level-shifting networks are possible, they degrade noise performance and nullify the OPA860ID's key advantages - TI explicitly characterizes and guarantees performance only under dual-supply conditions per SBOS331C.