Operational amplifiers (OPAMP) RM0440
792/2126 RM0440 Rev 4
Programmable gain amplifier mode with external filtering
The procedure to use the OPAMP to amplify the amplitude of an input signal, with an
external filtering, is presented hereafter.
• configure VM_SEL bits as “Feedback resistor is connected to OPAMPx_VINM input”,
10
• configure PGA_GAIN bits as “internal Gain 2, 4, 8, 16, 32 or 64 with filtering on
VINM0”, 10000 to 10101
• configure VP_SEL bits as “GPIO connected to OPAMPx_VINP”.
Any external connection on VINM can be used in parallel with the internal PGA, for
example a capacitor can be connected between opamp_out and VINM for filtering
purpose (see datasheet for the value of resistors used in the PGA resistor network).
Figure 174. PGA mode, internal gain setting (x2/x4/x8/x16/x32/x64),
inverting input used for filtering
1. The gain depends on the cut-off frequency.
STM32
+
-
INM0
MSv48042V1
VOUT
Allows optional
low-pass
filtering
(1)
Equivalent to
VINP3 or DACx_CHy
VINP2
VINP1
VINP0
opamp_out
(1)
1. opamp_out can be redirected internally to an ADC channel by setting OPAINTOEN bit.
In this case, the I/O on which is mapped the OPAMPx_VOUT is free and can be used for another purpose.
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