Contents
How is the resistance of an emitter follower calculated?
As it is normally used as a buffer amplifier, this is the key parameter. The input resistance can easily be calculated for a circuit because it is β times the resistor R1, where β is the forward current gain of the transistor. The simplest way of connecting an emitter follower is to directly couple the input as shown below.
What makes an emitter follower a common collector?
The emitter follower or common collector circuit configuration provides a high input impedance and a low output impedance. This means that the emitter follower circuit provides an ideal buffer stage,…
Can a emitter follower be driven from low impedance?
Emitter followers are notorious sources of oscillation and should never be directly driven from low impedance sources (again, see References 43 and 44). Marc T. Thompson Ph.D., in Intuitive Analog Circuit Design (Second Edition), 2014
How does an emitter follower transistor amplifier work?
The emitter follower transistor amplifier has a very straightforward circuit. The base is connected to the previous stage, and often this may be directly connected as this can save on additional bias resistors which lower the input impedance and hence increase the loading to the previous stage.
What is the low frequency voltage gain of an emitter follower?
We now find that the low-frequency voltage gain of the emitter follower is: Note that this gain is very close to unity if hfe RE >> R s, rx, and rπ. Next, we will find the output resistance rout of the emitter follower using the circuit in Figure 5.13. Initially, we will ignore the emitter resistance RE (and put it back in parallel later on).
How did the emitter follower amplifier get its name?
This name is derived from the fact that the emitter voltage “follows” that of the base circuit – the circuit has unit voltage gain. The emitter follower transistor amplifier has a very straightforward circuit.