What is the purpose of source degeneration resistor?

Source degeneration boosts the output impedance, but decreases the usable output swing.

What is a degeneration resistor?

One common way of alleviating these issues is with emitter degeneration. This refers to the addition of a small resistor between the emitter and the common signal source (e.g., the ground reference or a power supply rail).

What is the effect of degeneration resistor?

The emitter degeneration resistor helps linearize the small signal output. With emitter degeneration, the range of small signal input voltages over which the transfer function is approximately linear, is considerably widened.

How does common source amplifier work?

When the input signal is applied at the gate terminal and source terminal, then the output voltage is amplified and obtained across the resistor at the load in the drain terminal. This is called a common source amplifier. It produces current gain and voltage gain according to the input impedance and output Impedance.

What is the impact of source degeneration of common source amplifier?

As the input to the gate goes more positive the current through the degeneration resistor in the source circuit increases, reducing the gate-to-source voltage slightly. This is series negative feedback… it reduces the overall gain, increases linearity, and increases the amplifier’s effective output impedance.

What is degeneration in amplifier?

Emitter degeneration in an amplifier can be described as when all or part of an emitter resistor is not bypassed for ac or rf. R3a has no bypass capacitor while R3b is by-passed for a.c. or r.f. with a value in this particular instance of 0.82uF. Such a value assumes we are using it for audio or low rf frequencies.

What is the advantage of source resistor in a common source Mosfet amplifier?

These devices have the advantage over bipolar transistors of having an extremely high input impedance along with a low noise output making them ideal for use in amplifier circuits that have very small input signals.

What is the input resistance of common source amplifier?

The current-follower stage presents a load to the common-source stage that is very small, namely the input resistance of the current follower (RL ≈ 1 / gm ≈ Vov / (2ID) ; see common gate). Small RL reduces CM. The article on the common-emitter amplifier discusses other solutions to this problem.

What is the effect of degeneration resistance Rs on a CS amplifier?

Input resistance increase. Decrease of gain, but the reduced gain value is less dependent on transistor parameters (primarily determined by RD and RS) Bandwidth increase. Improved linearity (less total harmonic distortion)