Contents
What is stiff voltage divider bias?
A voltage divider in which the base current is small compared to the current in R2 is said to be a stiff voltage divider because the base voltage is relatively independent of different transistors and temperature effects.
What is emitter follower bias?
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 meant by bias voltage?
Overview. In electronics, ‘biasing’ usually refers to a fixed DC voltage or current applied to a terminal of an electronic component such as a diode, transistor or vacuum tube in a circuit in which AC signals are also present, in order to establish proper operating conditions for the component.
How do you know if a voltage divider is stiff?
What is stiff voltage source?
“Stiff source” means low source impedance, high ratio of prospective short circuit current / rated current, low effect of source voltage by changing load current. In the context to IEEE 519, notching is essentially a microsecond range short circuit caused by reverse recovery current of a thyristor.
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.
How to calculate a stiff voltage divider bias?
Step 1. Choose VE. For the largest possible symmetrical swing without clipping, VE = 0.5Vcc, or +7.5 volts. Step 2. Choose RE. For a quiescent current of 1mA, R E = 7.5k. Step 3. Choose Rl and R 2 . VB is VE+ 0.6, or 8.1 volts.
What is the Max Voltage for a follower?
Use a follower with base driven from a voltage divider to provide a stiff source of +5V from an available +15V supply. Load current (max) = 25 mA. Chose your resistor values so that the output voltage doesn’t drop more than 5% under full load.
Why is the base potential of an emitter resistor stiff?
It is the task of the emitter resistor Re to allow current-controlled voltage feedback. However, this works only in case the dc voltage at “other side” of the B-E path is kept constant (indpendent on temperature changes, tolerances and other uncertainties). That means that a “stiff” base potential is desired.