Advertisements
Advertisements
प्रश्न
With the help of a neat circuit diagram, explain the transistor as an amplifier?
Advertisements
उत्तर
Working of an amplifier:
- The circuit of an amplifier using an n-p-n transistor in CE configuration is shown in the figure.
- When the input voltage Vin is not applied, applying the Kirchhoff’s law to the output loop, we can write, VCC = VCE + ICRL
- Similarly, for input loop,
VBB = VBE + IBRB - When the input AC signal is applied, Vin is not zero. Thus, the voltage drop across the input loop will now be,
VBB + Vin = VBE + IBRB + ΔIB (RB + ri) ....(1) - The AC signal applied adds the current of ΔIB to the original current flowing through the circuit. Therefore, the additional voltage drop in the input loop will be across resistor RB (= ΔIBRB) and across the input dynamic resistance of the transistor (= ΔIBri).
- From equation (1),
Vin = ΔIB (RB + ri)
As, RB is very small, we can consider,
Vin = ΔIBri - The changes in the base current IB cause changes in the collector current IC. This changes the voltage drop across the load resistance because VCC is constant. We can write,
ΔVCC = ΔVCE + RLIC = 0
∴ ΔVCE = -RLIC - The change in the output voltage ΔVCE is the output voltage Vo hence we can write,
Vo = ΔVCE = `beta`ACRLΔIB
APPEARS IN
संबंधित प्रश्न
Why is the base of a transistor made thin and is lightly doped?
Why are the emitter, the base, and the collector of a BJT doped differently?
For a transistor β =75 and IE = 7.5 mA. The value of α is ______
In a transistor amplifier, IC = 5.5 mA , IE = 5.6 mA. The current amplification factor β is ______
The output of the following circuit is 1 when the input ABC is
In the circuit shown in the figure, the BJT has a current gain (β) of 50. For an emitter-base voltage VEB = 600 mV, calculate the emitter-collector voltage VEC (in volts).
A transistor has a voltage gain A. If the amount βA of its output is applied to the input of the transistor, then the transistor becomes oscillator, when ______.
If l1, l2, l3 are the lengths of the emitter, base and collector of a transistor, then ____________.
In switching circuit, transistor is in ON state. Values of IC and IB are 5.2 mA and 10 µA respectively and value of RC is 1 k`Omega`. If Vcc is at 5.5 V, then VCE is ______.
In an npn transistor, the collector current is 24 mA. If 80% of electrons reach collector, its base current in mA is ______.
In a transistor in CE configuration, the ratio of power gain to voltage gain is ____________.
In switching circuit, transistor is in ON state, values of IE and lB are 10 mA and 0.8 mA respectively and RL is 2 k`Omega`. If VCE is 7.6 V, then VCC is ____________.
For a common emitter configuration, if 'α' and 'β' have their usual meanings, the correct relationship between 'α' and 'β' is ______.
In a silicon transistor, a change of 7.89 mA in the emitter current if produces a change of 7.8 mA in the collector current, then the base current must change by ____________.
A transistor when connected in common emitter mode has a ____________.
A pnp transistor is used in common-emitter mode. If a change of 40 µA in base current brings a change of 2 µA in collector current with 0.04 V in base-emitter voltage, then the input resistance is ____________.
In a transistor, doping level in base is increased slightly, the collector current and base current respectively ______.
In common emitter amplifier, a change of 0.2 mA in the base current causes a change of 5 mA in the collector current. If input resistance is 2K `Omega` and voltage gain is 75, the load resistance used in the circuit is ______.
In a study of transistor as an amplifier, the ratio of collector current to emitter current is 0.98. The collector current is 3mA, then base current will be approximately ______.
A common emitter amplifier has a voltage gain of 50, an input impedance of 100Ω and an output impedance of 2000Ω. The power gain of the amplifier is ______.
A conducting wire has length 'L1' and diameter 'd1'. After stretching the same wire length becomes 'L2' and diameter 'd2' The ratio of resistances before and after stretching is ______.
In a p-n-p transistor circuit, the collector current is 10 mA. If 90% of the holes emitted from the emitter reach the collector, ______.
The reverse bias in a junction diode is changed from 8V to 13V, then the value of the current changes from 40μA to 60μA. The resistance of junction diode will be ______.
The current amplification factor for a transistor in its common emitter mode is 50. The current amplification factor in the common base mode of the transistor is ______.
Explain the working of the n-p-n transistor in a common base configuration.
In a CE amplifier, the current gain is 80 and the emitter current is 9 mA. The base current is ______.
When an n-p-n junction transistor is used as an amplifier in common emitter mode, ______.
In a transistor (common emitter configuration) the ratio of power gain to voltage gain is (α and β are current ratios) ______.
In the case of constants ‘α’ and ‘β’ of a transistor ______.
