OPA657U/2K5

The OPA657 device combines a high-gain bandwidth, low-distortion, voltage-feedback operational amplifier with a low-voltage noise JFET-input stage to offer a very high dynamic range amplifier for high-precision ADC (analog-to-digital converter) driving or wideband transimpedance applications. Photodiode applications see improved noise and bandwidth using this decompensated, high-gain bandwidth amplifier. Very low level signals can be significantly amplified in a single OPA657 gain stage with exceptional bandwidth and accuracy. Having a high 1.6-GHz gain bandwidth product gives greater than 10-MHz signal bandwidths up to gains of 160 V/V (44 dB). The very low input bias current and capacitance supports this performance even for relatively high source impedances. Broadband photodetector applications benefit from the low-voltage noise JFET inputs for the OPA657. The JFET input contributes virtually no current noise while for broadband applications, a low voltage noise is also required. The low 4.8 nV/√Hz input voltage noise provides exceptional input sensitivity for higher bandwidth applications. The example shown below gives a total equivalent input noise current of 1.8 pA/√Hz over a 10-MHz bandwidth.

Applications

• Wideband Photodiode Amplifier
• Wafer Scanning Equipment
• ADC Input Amplifier
• Test and Measurement Front End
• High Gain Precision Amplifier
• Optical Time Domain Reflectometry (OTDR)

Key features

• High Gain Bandwidth Product: 1.6 GHz
• High Bandwidth 275 MHz (G = 10)
• Slew Rate 700 V/µs (G = 10, 1-V Step)
• Available in High Grade With Improved DC Specifications
• Operating Temperature Range: -40°C to 85°C
• Low-Input Offset Voltage: ±250 µV
• Low-Input Bias Current: 2 pA
• Low-Input Voltage Noise: 4.8 nV/√Hz
• High-Output Current: 70 mA
• Fast Overdrive Recovery