In what part start midpoint or final stages of an IC circuit

In what part (start, mid-point, or final stages) of an IC circuit would you use a Common Source amplifier and why?

3. In IC circuits capacitors and large resistors are avoided, why?

4. What method(s) are used to bias amplifiers in IC design and why (see current sources)?

5. Why the active loads are used in IC design? Show an active load.

Solution

we use common source amplifier in the mid-point of an IC circuit. because like the bipolar common emitter amplifier the output of the Common Source JFET Amplifier is 180^o out of phase with the input signal. Midpoint biasing allows optimum ac operation of the amplifier.

3) In IC circuits capacitors and large resistors are avoided because they consume large areas. Resistors in IC have large amount of parasitic capacitance whereas capacitances are more voltage dependent.

4) There are different methods of simulating a dc current source for integrated circuit amplifier biasing. One type of current source used to provide a fixed current is the fixed bias transistor circuit. The problem with this type of current source is that it requires too many resistors to be practically implemented on IC. A simple current source and Widlar Current Source(Large resistors are often required to maintain small currents of the order of few µA and these large resistors occupy correspondingly large areas on the IC chip. It is therefore, desirable to replace these large resistors with current sources. One such device is the Widlar current source)

5) Many of the circuits used to generate bias currents are also used for providing large resistances for IC applications. The active loads created in this manner, as well as the dc current sources, are small and easy to fabricate on IC chips. To achieve this desirable load curve, we may use an active load, instead of a passive load, such as a resistor/ transistor etc.