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In synopsis, little increase in the base terminal will result in a large change in the collector terminal. If you input uer "small waveform" to the base terminal, u will have a "big waveform" at the output!
We kan bias the BJT using a DC voltage supply and resistors(most commonly and practically as potential divider bias). Note that this biasing should be done in order to achieve the active region of the BJT(B-E junction forward bias and B-C junction reverse bias such that VCE>VBE). In the active region, IC= hFE.IBwhere hFE (assume it as 100)denotes DC current gain or Beta, IC denotes the current towards the common terminal(C) and IB denotes the current towards the base terminal(B). Therefore, IC= 100IB. Whenever you change IB, IC will be changed in 100 times! That's how a BJT transistor has been constructed by modifying the p-n junction doping. Also that's simply how it amplifies....
What if we input an a.c. waveform(mid-frequency about 10kHz) which is smaller in magnitude through the base terminal(i.e. with the help of a coupling capacitor) and take the output across C and the ground (i.e. with the help of a coupling capacitor)?
Applying an alternating input across B-Ground results in chaniging the base voltage regularly(accordingly base current will also be changed). As explained earlier, change in the base current, will change the emitter current enormously(accordingly emitter voltage, VC). Hence voltage across C-Ground will be change largely. So uer input has been amplified!! As I mentioned earlier this output should be separated away across a coupling capacitor.
Note that, this amplification is happened with the help of the supply voltage to the transistor. Supply voltage is the one who provides energy to increase the amplitude of your small signal.
However, to analyse a BJT amplifier, we may have to perform both D.C analysis and a.c. analysis seperately[which will generally be teached in the Bachelors level].
Regards,
-R-
Wiki User
∙ 12y ago
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Which bjt transistor amplifier can be used as a voltage buffer?
the common collector can use as voltage buffer
Why bjt is called current controlled current device?
Because the operation of the transistor is determined by the current at the base. the principle equations of BJT operation are: Ic = h*Ib ,and Ie=Ib+Ic thus device operation is controlled by the input current.
Which BJT amplifier has the phase shift between input and output voltage is 180 degree?
The Class A common emitter BJT design has input on the base and output on the collector. This design is inverting, or 180 degrees phase shift.
What does gm0 represent in a BJT amplifier circuit?
gm0 is not used in BJT amplifier circuits; it is used in JFET circuits. It is the transconductance at zero gate bias. Since the transconductance varies as the bias is varied, this gives a benchmark level at a given defined point, and other transconductances can be calculated from it as a function of the amount of negative bias on the gate. If it were linear it would be the same everywhere, but it is not.
What are the advantages and disadvantages of JFET over BJT?
An advantage of JFET is stable high current operation. A disadvantage of JFET is low capacitance. An advantage of BJT is constant voltage operation. A disadvantage of BJT is low thermal conductance.
What is Cascaded BJT amplifier?
pinagdugtong na madaming amplifier
What are the steps involved in finding the signal gain for a common-emitter BJT amplifier?
The signal gain of a CE BJT amplifier is hFe or collector resistance divided by emitter resistance, whichever is less.
Which bjt transistor amplifier can be used as a voltage buffer?
the common collector can use as voltage buffer
What is the difference between normal amplifier and magnetic amplifier?
normal amplifier is a mathametical operation analog the computer, magnetic amplifier is sound operation of the signal
What is the explanation for the working CE BJT amplifier?
In electronics, a common-emitter amplifier is one of three basic single-stage bipolar-junction-transistor (BJT) amplifier topologies, typically used as a voltage amplifier. In this circuit the base terminal of the transistor serves as the input, the collector is the output, and the emitter is common to both (for example, it may be tied to ground reference or a power supply rail), hence its name.
Why bjt is called current controlled current device?
Because the operation of the transistor is determined by the current at the base. the principle equations of BJT operation are: Ic = h*Ib ,and Ie=Ib+Ic thus device operation is controlled by the input current.
What 3 things does an electrical amplifier amplify?
An electrical amplifier amplifies 2 physical quantities according to the transistors used. If a BJT is used it amplifies the current and if a MOSFET is used it amplifies the voltage. Hybrid amplifiers amplify current as well as voltage so in theory , current voltage and power is amplified.
What is the expected amplification of a BJT transistor amplifier if the dc supply is set zero volts?
very simple, zero.
Why use a npn transistor in a common emitter bjt single stage amplifier circuit?
You can use an npn or a pnp bjt in a common emitter amplifier circuit. The decision of which one to use is based on whether you want the collector and base to be more positive (npn) or more negative (pnp) than the emitter.
How BJT works as a amplifier?
aplied weak input signal is amplied at output side due to very high resistence
Which BJT amplifier has the phase shift between input and output voltage is 180 degree?
The Class A common emitter BJT design has input on the base and output on the collector. This design is inverting, or 180 degrees phase shift.
How do you design a RC coupled bjt amplifier using pnp transistor?
same as you would using an NPN, except the supply voltages are reversed
