Operational amplifier is ideal for wideband transimpedance circuits

16-07-2019 | Texas Instruments | Power

The OPA855 decompensated amplifier from Texas Instruments is intended as a wideband, low-noise, bipolar-input operational amplifier. The device shines in high bandwidth transimpedance and voltage amplifier applications. The 8GHz GBWP of the device allows high-gain configurations while supporting wide closed-loop bandwidth. Further, the low input-voltage noise of 0.98nV/√Hz reduces noise contribution from the amplifier, and the high slew rate of 2750V/µs allows wide output voltage swings.


For TIA applications the device features a low input capacitance of only 0.8pF, which reduces the total circuit input capacitance and allows higher-speed designs. The device also employs a unique package pinout that simplifies the layout of the feedback network whilst concurrently isolating pin-to-pin capacitance between the input and feedback connections. This pinout design decreases the whole parasitic capacitance around the amplifier’s feedback network, providing for high-gain TIA designs to deliver wide bandwidth.


TIA applications for the device include in optical ToF systems with a time-to-digital converter, such as the company's TDC7201. Alternatively, the device can also be utilised to drive a high-speed ADC in high-resolution LIDAR systems with a differential output amplifier, such as their THS4541 or LMH5401.


This latest addition to the family of ultra-wide bandwidth operational amplifiers also incorporates the FET-input OPA858 and OPA859 devices. This family of amplifiers is perfect 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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