Texas Instruments OPA689P

Overview

OPA689P from Burr-Brown (now Texas Instruments) is a wideband voltage-feedback operational amplifier with integrated bipolar output voltage limiting, stable for gains ≥ +4. It delivers ±15mV limiter accuracy, 280MHz –3dB bandwidth at G = +6, 1600V/µs slew rate, and 2.4ns recovery from overdrive - enabling precision fast-limiting ADC input drivers and IF limiting amplifiers in communications infrastructure.

For engineers reviewing the OPA689P datasheet, OPA689P pinout, OPA689P application, or OPA689P equivalent, key selection criteria include limiting voltage accuracy under varying common-mode conditions, recovery time consistency across temperature, stability margin at minimum gain, and limiter feedthrough rejection at RF frequencies.

Technical Context

The OPA689P implements output-stage limiting via dedicated VH and VL pins that directly control a buffered output stage, decoupling limiter accuracy from closed-loop gain configuration. Its decompensated architecture ensures stability only at G ≥ +4, trading unity-gain capability for higher bandwidth (280MHz), faster slew (1600V/µs), and lower noise (4.6nV/√Hz) versus the OPA688.

Limiter operation is characterized by sharp linear-to-limit transition (30mV guardband), 450MHz small-signal bandwidth in limit mode, and <2.4ns recovery - achieved through independent limiter bias paths with 2MΩ || 1pF input impedance and ±70µA max bias current at ±5V supply.

Key Specifications

Pinout & Package

OPA689P is housed in an 8-pin PDIP package with industry-standard op amp pinout and through-hole mounting compatibility.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voltage limiting amplifier applications.

Compared with OPA688P and LMH6720MF, the OPA689P uniquely balances 280MHz bandwidth, ±15mV limiter accuracy, and 2.4ns recovery - making it optimal for gain-stable, high-fidelity limiting in IF and ADC driver roles where both speed and clipping precision are non-negotiable.

Availability

OPA689P is available at Aetrix Electronics and suitable for optical receiver front-ends, high-speed data acquisition systems, RF test instrumentation, and cellular infrastructure requiring stable component supply with traceable lot history and extended lifecycle support.

Supply support for OPA689P 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

Burr-Brown Corporation, acquired by Texas Instruments in 2000, specialized in high-performance analog ICs including precision op amps, data converters, and interface solutions.

The OPA689P belongs to Burr-Brown's wideband limiting amplifier product line, engineered specifically for applications demanding simultaneous high speed, accurate amplitude limiting, and fast overdrive recovery in communications and instrumentation signal paths.

FAQ

What is the minimum stable gain for the OPA689P?

The OPA689P is decompensated and guaranteed stable only for closed-loop gains ≥ +4. Attempting unity-gain or G = +2 configurations will cause peaking or oscillation. This design choice enables its 280MHz bandwidth and 1600V/µs slew rate - significantly exceeding unity-gain-stable alternatives like the OPA688P. Always verify phase margin with actual PCB parasitics using the recommended 750Ω feedback resistor.

How does limiter accuracy vary with temperature for the OPA689P?

The OPA689P maintains ±15mV limiter offset voltage (VO – VH or VO – VL) over the full –40°C to +85°C operating range, with worst-case degradation to ±40mV at +85°C per datasheet Section "DC Performance in Limit Mode". This tight tolerance is enabled by matched internal limiter circuitry and remains independent of gain configuration - a key advantage over externally clamped amplifiers whose accuracy drifts with diode V_F temperature coefficients.

Can the OPA689P operate from a single +5V supply?

Yes, the OPA689P supports single +5V operation with VCM = 2.5V, where VH and VL are set relative to common-mode voltage (e.g., VH = VCM + 1.2V, VL = VCM – 1.2V). In this mode, output swing is reduced to ±1.6V (min) into 500Ω, and limiter separation must remain ≥200mV. The device draws 13mA (min) quiescent current - lower than dual-supply operation - making it viable for portable instrumentation where rail efficiency matters.

What is the maximum capacitive load the OPA689P can drive without instability?

The OPA689P requires series isolation resistance (R_S) when driving capacitive loads >2pF. Per the "RS vs Capacitive Load" curve (Figure 8), a 125Ω R_S is recommended for 100pF loads, and 150Ω for 1000pF. Without R_S, even 10pF loads cause gain peaking; 1000pF directly causes oscillation. This behavior stems from its high open-loop gain and limited phase margin - always simulate with actual PCB trace capacitance and use the recommended R_S/C_L combinations from the datasheet.

Does the OPA689P require external compensation components?

No, the OPA689P is internally compensated for stability at G ≥ +4 and requires no external capacitors for basic operation. However, the "RS vs Capacitive Load" plot mandates series output resistance for driving cables or ADC inputs with significant capacitance. Also, the transimpedance application (Figure 6) uses CF = 1.0pF and CD = 5.0pF for photodiode stabilization - but this is application-specific, not general-purpose compensation. Always follow layout guidelines: 0.1µF ceramic bypass caps <0.2" from each supply pin and ground-plane isolation around I/O pins.