# Op-amp gives attenuated output

I am using an OPA547 high voltage and high current op-amp.

• V+ = 15 V
• V- = GND or -15 V
• Ilim is shorted with V-
• Vout has a fb resistor of 1K. The output load is a 50-ohm resistor
• Vin+ = 0 V (GND)
• Vin- is connected to 2 Vpp 1 KHz sine with dc offset -2.5 V through a 1K resistor

I am using it as inverting amplifier with unity gain. The expected output is supposed to be a sine signal with 2 Vpp with an offset of +2.5 V, but the actual output is

Case i) V+ = +15 V and V- = GND

Case ii) V+ = +15 V and V- = -15 V

Can anyone guess what could be the problem?

• Vin+ must be at a higher voltage, you have grounded the gate of one side of your diff. pair and left no room for the current source since everything is at 0 volts. To give you a hint, measure the voltage at your virtual ground. Commented Oct 15, 2022 at 12:40
• One detail you should disclose is the frequency of the input sine wave. Commented Oct 15, 2022 at 12:43
• There is a schematic editor built in to the editor. It is fairly easy to use. The icon looks like components in parallel or Ctrl-M is the hotkeys. Commented Oct 15, 2022 at 12:57
• @ErnestoG The voltage at Vin+ is 0 V. Do you suggest connecting Vin+ to GND through a 1k resistor? Commented Oct 15, 2022 at 13:07
• @KishoreKumarS, no. What you need to do is define the common-mode voltage of your input. I asked for the voltage at V-. Commented Oct 15, 2022 at 13:16