Chapter 2: Further mains power supply Flashcards
What is line regulation?
Measures the ability of the power supply to maintain a steady output voltage when the output line voltage changes
What is load regulation?
Measures the ability of the output voltage to remain constant when the output current changes due tot a change in load
What does an emitter follower do?
Improves the performance of a zener voltage regulator
Draw an emitter follower circuit
See ntoes for diagram
For an emitter follower circuit, how would you calculate Vout?
Vout=Vs-0.7V
Tell me one thing about the input and output current in an emitter follower?
Iout>Iin which means it acts as a buffer
Draw an emitter follower circuit which has a regulated power supply
See in notes for diagram
How is the current different for a regulated power supply emitter follower from a regular emitter follower?
There is a lower current through the base in a regulated power supply emitter follower. This means there is a lower current through the resistor
How is the power different for a regulated power supply emitter follower from a regular emitter follower?
The power dissipated in the resistor and zener diode is less, even with no load
State one way that load regulation can be improved for an emitter follower
Using an op amp to provide negative feedback
Draw the circuit of a emitter follower which provides negative feedback?
See notes for details
How does the emitter follower with negative feedback work
Op-amp keeps both inputs the same when not in saturation, so V1= VZ .
It does this because VO = A0× (VZ – V1) when not saturated, where A0 = Open loop gain.
If VOUT falls, then V1 falls.
The difference between the op amp inputs increases because VZ-V1
Give the voltage divider for a emitter follower that provides negative feedback
Vout=Vz(Rf+R1)/R1
Draw a voltage regulator circuit
See notes for details
What is ‘holding current’?
The minimum output to keep Vz.
(Vz drops otherwise)
