Why common collector is used for impedance matching?

Common collector configuration, also known as emitter follower provides high input impedance and low output impedance. So they are used for the purpose of impedance matching. The current gain in the common-collector configuration is therefore the ratio of the emitter current to the base current.

Which is most suitable for impedance matching?

Explanation: CC has high input impedance and low output impedance. Hence suitable for impedance matching.

How is impedance matching done in a common collector circuit?

Impedance matching is done with passive components. A common-collector circuit is good at providing a high input impedance (to a weak signal) and generating a low output impedance (at the emitter) – it is a power amplifier not an impedance matcher.

Which is the best circuit for impedence matching?

A common-collector circuit is good at providing a high input impedance (to a weak signal) and generating a low output impedance (at the emitter) – it is a power amplifier not an impedance matcher. See let us take an example for a basic analog circuit where the voice signal is amplified and sent to the loudspeaker.

Why are common collector transistors used for voltage matching?

As per we know common collector have high input resistance and low output resistance. Due to this reason this type of circuits especially used for impedance matching i.e. for driving low impedance load from high impedance source. Common collector circuit provides high voltage gain but this circuit is not able to give high current gain.

Why is a common collector circuit not suitable for amplification?

Common collector circuit has a very high input impedance and very low output impedance so voltage gain provides by this type of circuit is less than 1. Because of that, this type of circuit is not that much suitable for amplification.

Why common-collector is used for impedance matching?

Common collector configuration, also known as emitter follower provides high input impedance and low output impedance. So they are used for the purpose of impedance matching. The current gain in the common-collector configuration is therefore the ratio of the emitter current to the base current.

Why does common-collector have high input impedance?

Input impedance is base to ground. For a CC ground and collector have the same AC value. There is a secondary effect though as the emitter resistance Re changes with bias current, (current is a function of Re + Rload) so input impedance does change with different bias conditions and for very large voltage excursions.

Why are the capacitances of a BJT so small?

There are very small capacitances in a BJT between the collector and the base, and the base and the emitter. Since the capacitor values are very small, their impedance at low and moderate frequencies is large.

How is the impedance of a common collector used?

The Low output impedance of the common-collector is put to good use in impedance matching, for example, transformerless matching to a 4 Ohm speaker. There do not appear to be any simple formulas for the output impedances. However, R. Victor Jones develops expressions for output resistance.

What is the output impedance of a common emitter?

The moderate output impedance of the common-emitter configuration helps make it a popular choice for general use. The Low output impedance of the common-collector is put to good use in impedance matching, for example, transformerless matching to a 4 Ohm speaker. There do not appear to be any simple formulas for the output impedances.

What is the effect of an emitter follower?

• Emitter follower lowers the source impedance by a factor of β+1 Æimproved driving capability. • Since rO is in parallel with RE, its effect can be easily incorporated into voltage gain and input and output impedance equations. • There is a current gain of (β+1) from base to emitter.