What is the effect of collector resistor in emitter follower amplifiers?
Common Collector Input Impedance Another useful feature of the common collector amplifier is that it provides current gain (Ai) as long as it is conducting. That is it can pass a large current flowing from the collector to the emitter, in response to a small change to its base current, IB.
What are the three most important characteristics of an emitter follower?
The important characteristic of emitter-follower is
- high input impedance and high output impedance.
- high input impedance and low output impedance.
- low input impedance and low output impedance.
- low input impedance and high output impedance.
What is HFE in a transistor?
hFE is an abbreviation, and it stands for “Hybrid parameter forward current gain, common emitter”, and is a measure of the DC gain of a junction transistor. So on a multimeter, it indicates a mode where the meter can measure (probably crudely), the HFE of a transistor.
What are the characteristics of emitter follower?
Emitter Follower
- It has high input impedance.
- It has low output impedance.
- It is ideal circuit for impedance matching.
What is the difference between hFE and HFE?
hfe and HFE are two different, but related, characteristics of a bipolar transistor. hFE is the short circuit (vCE=0) forward current ratio (also known as h21) at a specified DC bias (which must be stated for each value of hFE). hfe is the small signal AC gain at a specified bias, and is frequency dependent.
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.
Can a common collector buffer be coupled to an emitter follower?
It is not always possible to directly couple the emitter follower, common collector buffer. When this is the case, it is necessary to add a few additional electronic components: coupling capacitors and bias resistors to the circuit.
Why does the common emitter have lower output resistance than the emitter?
Due to the unity gain of the voltage gain follower, is approximately the same as the source voltage . Comparing this with the output resistance of the common-emitter circuit , we see that the emitter follower has much lower output resistance.
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.