Frequency

8GHz op amp enables high-gain configurations

5th July 2019
Mick Elliott

Designed as a wideband, low-noise, bipolar-input operational amplifier, the OPA855 decompensated amplifier from Texas Instruments (TI) excels in high bandwidth transimpedance and voltage amplifier applications. The 8GHz gain-bandwidth product (GBWP) of the OPA855 enables high-gain configurations while maintaining wide closed-loop bandwidth.

Additionally, the low input-voltage noise of 0.98nV/√Hz minimises noise contribution from the amplifier, and the high slew rate of 2750V/µs enables wide output voltage swings.

For transimpedance amplifier (TIA) applications the device, which is available from Mouser Electronics, features a low input capacitance of only 0.8pF, which minimises the total circuit input capacitance and enables higher-speed designs.

It also uses a unique package pinout that simplifies the layout of the feedback network while simultaneously isolating pin-to-pin capacitance between the input and feedback connections.

This pinout design reduces the total parasitic capacitance around the amplifier’s feedback network, allowing for high-gain TIA designs to achieve wide bandwidth.

TIA applications for the op amp include in optical time-of-flight (ToF) systems with a time-to-digital converter, such as TI’s TDC7201.

Alternatively, it can also be used to drive a high-speed analogue-to-digital converter (ADC) in high-resolution LIDAR systems with a differential output amplifier, such as TI’s THS4541 or LMH5401.

The OPA855 is the latest addition to TI’s family of ultra-wide bandwidth operational amplifiers, which also includes the FET-input OPA858 and OPA859 devices.

This family of amplifiers is ideal for wideband transimpedance circuits as well as high-speed data acquisition systems, low-noise front ends, and more.

The device is supported by the dedicated OPA855DSGEVM op amp evaluation module and the general-purpose DEM-OPA-WSON8-EVM unpopulated evaluation board.

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