Transistors Circuits
Transistor
A small electronic device used in a circuit as an amplifier, switch and oscillator.
NPN Transistor
A transistor that has two N-type semiconductors and one P-type semiconductor bonded together
A base in a transistor does what?
Allows some current to pass between the emitter and the collector
Disadvantages of Direct coupling (3)
At high frequency amplification cannot be achieved,, efficiency is less (dc) power loss, Poor Q point stability
Disadvantages of Transformer coupling (3)
Bulky, Costly, More space, Frequency distortion high
common emitter circuit (4)
Emitter is common in both circuits, Mid range current and voltage gain, High power gain, Input signal is inverted for output
Advantages of Transformer coupling (4)
Excellent impedance matching, No loss of signal (DC) power, High gain
Disadvantages of RC coupling (3)
Not good for impedance matching, Not great gain ( Voltage, Power), High noise
Types of coupling in Multi stage Amplifier (3)
RC, Transformer, Direct
A emitter in a transistor does what?
Sends the output voltage
Advantages of Direct coupling (4)
Simple Circuit, low cost, Good Frequency, Good impedance matching
Advantages of RC coupling (4)
Simple, Cost effective, Less space & weight, used in AF range
PNP Transistor
Thin Piece of N-type between two P-Type Materials; negative voltage applied
Voltage Divider
Two resistors are used to divide voltage, Emitter is shared
Active mode (amplifier)
Vb is equal to 0.7, Ib is between 0 and mx current, Vc and Ve is between 0 and max voltage
In Saturation mode a transistor
acts like a short circuit. Current freely flows from collector to emitter
In Cut off mode a transistor
acts like an open circuit. No current flows from collector to emitter
A collector in a transistor does what?
collects electricity
Uses of a transistor
electronic switch, oscillators and amplifiers
Disadvantages of Self Bias
negative feedback, reduces gain of amplifier
Disadvantages of Fixed Bias
poor stabilization, strong chances of thermal runaway
As you add stages bandwidth will ____ and your gain will ______
reduce, increase
Advantages of self Bias
simple, High stability, gets its own voltage
Advantages of Fixed Bias
simple, less components, bias conditions are easily set
Transistors are biased by
supplying Base with a control amount of voltage and current in order for it to work
Transistor that is not properly bias
will not work properly