IC MOSFET AMPLIFIERS
1. Define an Integrated circuit.
An integrated circuit(IC) is a miniature ,low cost electronic circuit consisting of active and passive components fabricated together on a single crystal of silicon.The active components are transistors and diodes and passive components are resistors and capacitors.
2. What are the advantages of ICs over discrete circuits.?
1. Minimization & hence increased equipment density.
2. Cost reduction due to batch processing.
3. Increased system reliability
4. Improved functional performance.
5. Matched devices.
6. Increased operating speeds
7. Reduction in power consumption
3. List the disadvantages of ICs
• Inductors cannot be fabricated
• IC function at very low voltage
• Limited amount of power
• Excessive heat
4. Define steering current.
In integrated circuit designs circuits use constant sources.here the constant d.c current called reference current is generated at one location and is then replicated at various other locations for biasing the various stages of amplifier present in the circuit. this process is known as current steering.
5. State the advantages of current steering?
• The external components such as precision resistors required to generate a predictable and stable reference current,need not be repeated for every amplifier stage.
• The bias currents of the various stages track each other when there is any change due to power supply voltage or temperature.
6. Define cascade current mirror circuit.
MOSFET current source circuits the output resistance is a measure of stability of Io with respect to the changes in the output voltage. Here MOSFET T3 andT4 are included to provide higher output resistance. This circuit is known as cascade current mirror circuit.
7. Define Wilson current mirror circuit?
MOSFET Wilson current source the VDS values of T1 and T2 are not equal. Since λ is not zero, the ratio Io/Iref is slightly different from the aspect ratio.
8. State the advantages of Wilson current mirror circuit.
The advantages of these circuits are the increase in output resistance and hence increase the stability of output current.
9. List the various types of active loads?
There are three types of load devices:
• N-channel enhancement mode device
• N-channel depletion-mode device
• P-channel enhancement mode device
10. State the advantages of NMOS amplifier with depletion load over enhancement load.
The voltage gain of NMOS amplifier with depletion load is significantly larger than that
with the enhancement load, however, like NMOS amplifier with enhancement load, the body effect lowers the small-signal voltage gain.
11. Define β and α.
• α is a current gain which is the ratio of collector current to the base current.
• β is a forward current gain which is the ratio of collector current to the emitter current.
12. What is meant by over drive factor?
The over drive factor is defined as the ratio of IB and IBS. Where, IB is the base current and IBS is the base current that produces the saturation.
13. Define delay time.
During the delay time period, base emitter voltage VBE is applied, the base current IB rises to IBS and the collector current IC is equal to zero or collector emitter leakage current ICEO. The time required to charge the base emitter capacitance to, VBES=0.7 V.
14. Define rise time.
During the rise time period, collector current IC raises to steady state values ICS and the collector emitter voltage falls from VCC to VCES the rise time depends on the input capacitance.
15. What is the need of driver circuit?
9 It provides amplified voltage and current to the device.
9 It provides isolation between control circuit and power circuit.
16. State methods which are used to provide effect of increased RE.
• Constant current bias method
• Use of current mirror circuit
• Use of an active load.
17. What is current mirror ?
The circuit in which the output current is forced to equal the input current is called as current mirror circuit. In a current mirror circuit, the output current is the mirror image of input current.
18. State advantages of current mirror circuit. 1)Provides very high emitter resistance RE. 2)Easy to fabricate.
3)Requires less components then constants current bias. 4)Simple to design
5)With properly matched transistors,collector current thermal stability is achieved.
19. What are the types of internal capacitance in the MOSFET?
There two types of
20.Define gate capacitance.
It is a parallel plate capacitance formed by a gate electrode with the channel with the oxide layer acts as a capacitor dielectric. It is denoted as Cox.
21. List the advantage of active load.
• provides very high ac resistance
• provides high differential mode voltage gain
• Ad High
• CMRR High