Op-Amp Buffer, Inverting & Non-Inverting Configurations
An op-amp buffer, or voltage follower, provides high input and low output impedance, isolating circuit stages without amplifying voltage. In the inverting configuration, the input signal is applied to the inverting terminal, producing an output 180 degrees out of phase with gain set by resistor ratios. The non-inverting configuration applies input to the non-inverting terminal, yielding an output in phase with the input and similar gain control, useful for signal amplification and conditioning.
Op-Amp Buffer, Inverting & Non-Inverting Configurations
An op-amp buffer, or voltage follower, provides high input and low output impedance, isolating circuit stages without amplifying voltage. In the inverting configuration, the input signal is applied to the inverting terminal, producing an output 180 degrees out of phase with gain set by resistor ratios. The non-inverting configuration applies input to the non-inverting terminal, yielding an output in phase with the input and similar gain control, useful for signal amplification and conditioning.
💡 Key Takeaways
- Understand the op-amp buffer (voltage follower): unity gain with high input impedance and low output impedance.
- Describe the inverting configuration: negative feedback, virtual ground at the input, gain set by -Rf/Rin.
- Describe the non-inverting configuration: input at the + terminal, gain = 1 + Rf/Rin, and high input impedance.
- Compare configurations: gain and phase (buffer/non-inverting preserve phase, inverting flips phase), impedance, and typical uses.
❓ Frequently Asked Questions
What is an op-amp buffer (voltage follower)?
A configuration with the output tied to the inverting input. The output voltage follows the input (gain ≈ 1) while input impedance is very high and output impedance is low.
How does the inverting amplifier configuration work?
Input signals pass through Rin to the inverting input, with Rf from output back to the inverting input. The non-inverting input is at ground. Closed-loop gain is -Rf/Rin (inverted signal, magnitude set by resistor ratio).
How does the non-inverting amplifier configuration work?
The input is applied to the non-inverting input. The inverting input is fed by a voltage divider of Rf and R1 from the output. The gain is 1 + (Rf/R1); no phase inversion and high input impedance.
When should you use each configuration?
Use a buffer to isolate a source and drive a load without loading it. Use an inverting amplifier when you need gain with inversion and a defined input impedance (≈ Rin). Use a non-inverting amplifier when you need gain with high input impedance and no inversion; consider real-world limits like finite bandwidth and bias currents.