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SBOU252 August 2021 OPA4991 , OPA4991-Q1 , TLV9004 , TLV9004-Q1

4.4 Inverting Amplifier

Figure 4-7 shows the schematic for the inverting amplifier circuit configuration. To configure the EVM in an inverting configuration short R_INP using a 0-Ω resistor or solder bridge, leave R_VREF and C_VREF unpopulated, and apply the desired common mode voltage(VCM) to the input connection, IN+. The input signal is applied using the input connection IN–.

Figure 4-7 Inverting Amplifier Schematic

Table 4-4 Inverting Amplifier Components

CH	R_INM	R_F	C_F	R_INP	R_Iso	C_L
1	R1	R2	C3	R3	R5	C5
2	R7	R8	C6	R9	R11	C8
3	R13	R14	C9	R15	R17	C11
4	R19	R20	C12	R21	R23	C14

Equation 6 displays the DC transfer function for channel 1 of the inverting amplifier circuit configuration. Note, Input signals IN+ and IN- are altered to IN_P and IN_M respectively in the transfer function for simplicity of the equation.

Equation 6.

OUT = - \frac{R_{F}}{R_{INM}} \times {IN}_{M} + (1 + \frac{R_{F}}{R_{INM}}) \times {IN}_{P}

Capacitor C_F provides the option to filter the output. The cutoff frequency, f_c, of the filter can be calculated using Equation 7.

Equation 7.

f_{c} = \frac{1}{2 \times π \times R_{F} \times C_{F}}

Resistor R_iso, and capacitor C_L provide the option to create a RC filter, or test output loads for the amplifier. When not applicable, use a zero ohm resistor for R_iso and do not populate C_L.

Figure 4-8 shows the DYY-AMP-EVM populated with the required components to configure channel 1 as an inverting amplifier with no load.

Figure 4-8 Inverting Amplifier Configured on DYY-AMP-EVM, Channel 1

CH	R_INM	R_F	C_F	R_INP	R_Iso	C_L
1	R1	R2	C3	R3	R5	C5
2	R7	R8	C6	R9	R11	C8
3	R13	R14	C9	R15	R17	C11
4	R19	R20	C12	R21	R23	C14

CH	R_INM	R_F	C_F	R_INP	R_Iso	C_L
1	R1	R2	C3	R3	R5	C5
2	R7	R8	C6	R9	R11	C8
3	R13	R14	C9	R15	R17	C11
4	R19	R20	C12	R21	R23	C14

CH	R_INM	R_F	C_F	R_INP	R_Iso	C_L
1	R1	R2	C3	R3	R5	C5
2	R7	R8	C6	R9	R11	C8
3	R13	R14	C9	R15	R17	C11
4	R19	R20	C12	R21	R23	C14