A single-ended differential amplifier is a circuit that amplifies the difference between two input signals, while rejecting any common mode signal that is present on both inputs.

The voltage gain of a single-ended differential amplifier can be increased by increasing the value of the feedback resistor or reducing the value of the input resistor. However, care must be taken to ensure that the amplifier remains stable and does not oscillate.

When the signal is given to the T1 and T2 is ground. T1 acts like a CE amplifier. So that a complicated and inverted signals appears at its collector. But T2 acts like co amplifier and equally amplified and in phase signal appears across its collector.

Since re is ideally infinite

The equation Av = -Rc/2re represents the voltage gain of a single-ended differential amplifier in degeneration mode, where the gain is determined by the ratio of the collector resistance (Rc) to twice the emitter resistance (2re). The negative sign indicates that the output signal is inverted with respect to the input signal.

It is worth noting that the voltage gain given by this expression is typically much lower than that of a non-degenerated single-ended differential amplifier, and is also lower than that of a fully differential amplifier. Therefore, this configuration is typically used in applications where a moderate level of gain is required, and where the stability and linearity of the amplifier are important considerations.

The voltage gain of a single-ended differential amplifier is important because it determines the sensitivity of the amplifier to changes in the input signal. A higher voltage gain means that the amplifier is more sensitive to changes in the input signal, which can be useful in applications where small signals need to be amplified, such as in sensor or instrumentation circuits.

Additionally, the voltage gain of a single-ended differential amplifier can be used to control the output signal level and adjust the gain of the overall system. For example, in audio amplifier circuits, the voltage gain can be adjusted to control the volume of the output signal.

Furthermore, the voltage gain of a single-ended differential amplifier is an important parameter to consider when designing the amplifier circuit, as it can affect the stability, distortion, and noise performance of the amplifier. A high voltage gain can lead to increased distortion and noise, while a lower voltage gain can improve the stability and linearity of the amplifier.

This note is a part of the Physics Repository.

Previous topic: Differential gain and Common mode gain

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