STM32U5 OPAMP usage with sine wave with voltage offset

[Seokjin]

Hello ST.

I would like to amplify a signal using the built-in opamp of the STM32U575ZIT6QU or STM32U575RGT6 product.

The signal I want to amplify is as follows:

• The middle voltage is approximately 1.65V,
• It has an normal amplitude in the range of 1.5V to 1.8V,
• I would like to amplify this amplitude to a level such as 1V to 2.3V.

Is it possible to use the built-in op-amp in this scenario?

I would prefer to first consider using the PGA connected mode without external resistors or capacitors.

It would be greatly appreciated if you could provide detailed information on how to connect the circuit.

Thanks in advance.

[Sarra.S]

Hello @Seokjin, 

The gain can be set using the OPAMP_CSR register, you can find the sequence to follow in the RM: 

The procedure to use the OPAMP to amplify the amplitude of an input signal is presented hereafter (all bits in OPAMPx_CSR):
1. Set OPAMODE[1:0] to 10 (internal PGA enabled).
2. Set PGA_GAIN[1:0] to the selected PGA gain (2, 4, 8 or 16) in OPAMPx_CSR.
3. Set VM_SEL[1:0] to 1x in OPAMPx_CSR (inverting input not externally connected).
4. Clear VP_SEL to 0 in OPAMPx_CSR (GPIO connected to VINP).
5. As soon as OPAEN is set in OPAMPx_CSR, the signal on the OPAMP_VINP pin is amplified by the selected gain and visible on the OPAMP_VOUT pin

Connect the input signal to the non-inverting pin of the OPAMP.