Inverting and Non-inverting Amplification of Operational Amplifiers

Jul 14, 2025#电路23

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The document discusses operational amplifiers (op-amps) focusing on inverting and non-inverting amplifiers. 1. **Inverting Amplifier**: When the non-inverting terminal is grounded (0 V), the inverting terminal also approximates 0 V due to virtual shorting, leading to a relationship between input and output voltages given by \( V_{out} = -\frac{R_2}{R_1} \times V_i \). 2. **Non-Inverting Amplifier**: Similarly, the relationship for the non-inverting amplifier is \( V_{out} = \frac{R_1 + R_2}{R_2} \times V_i \). 3. **Advantages and Disadvantages**: - **Inverting Amplifier**: - Advantages: Low input voltage (close to 0 V), strong noise immunity. - Disadvantages: Low input impedance, equal to the series resistance at the input. - **Non-Inverting Amplifier**: - Advantages: High input impedance. - Disadvantages: Higher common-mode voltage, weaker noise immunity, requiring a high common-mode rejection ratio. For applications needing low input impedance and no phase requirements, the inverting amplifier is preferred due to its strong noise immunity and larger input signal range. When designing for the same gain, using smaller resistor values is recommended to minimize input bias current and parasitic capacitance effects.

1 Inverting Amplifier#

The non-inverting terminal is grounded, with a voltage of 0. The inverting and non-inverting terminals are virtually shorted, so the voltage is also 0 V. At the same time, due to the virtual break, there is almost no current injected, so R1 and R2 are equivalent to being in series, and the current through the resistors is equal.

Thus, the input-output relationship can be expressed as

V_{out}=-\frac{R_2}{R_1}\times V_i

2 Non-Inverting Amplifier#

Similarly, based on the virtual break and virtual short, the input-output relationship can be expressed as

V_{out}=\frac{R_1+R_2}{R_2}\times V_i

3 Advantages and Disadvantages of Non-Inverting and Inverting Amplifiers#

3.1 Inverting Amplifier#

Advantages: The potentials at the two input terminals are always approximately 0, with only differential mode signals, providing strong anti-interference capability.
Disadvantages: The input impedance is low, equal to the series resistance value of the signal to the input terminal.

3.2 Non-Inverting Amplifier#

Advantages: The input impedance is close to infinity.
Disadvantages: The amplification circuit does not have a virtual ground, has a large common-mode voltage, poor anti-interference capability, and requires the operational amplifier to have a high common-mode rejection ratio during use.

If a low input impedance is acceptable and there are no phase requirements, the inverting amplifier is preferred because it only has differential mode signals, providing strong anti-interference capability and allowing for a larger input signal range.

In designs requiring the same amplification factor, it is advisable to choose smaller resistor values to minimize the effects of input bias current and distributed capacitance.