BiCMOS Inverter and BJT Types

BiCMOS inverter is a combination of bipolar and CMOS technologies. It is used to achieve high speed and low power consumption. In this inverter, the input signal is applied to the gate of a MOSFET and the output signal is taken from the collector of a bipolar junction transistor (BJT).

BJTs are used in BiCMOS inverters to provide high gain and high output current. There are two types of BJTs: NPN and PNP. However, in BiCMOS inverters, only NPN BJTs are used.

Reasons for Using NPN BJTs

1. Compatibility with CMOS: The main reason for using NPN BJTs in BiCMOS inverters is their compatibility with CMOS technology. Both NPN BJTs and CMOS transistors can be fabricated on the same silicon substrate using the same process steps. This simplifies the manufacturing process and reduces the cost of production.

2. High Gain: NPN BJTs provide high gain, which is necessary for amplification and signal processing. The gain of an NPN BJT is typically in the range of 50 to 300.

3. High Output Current: NPN BJTs can provide high output current, which is necessary for driving capacitive loads and other high-current devices.

4. Low Saturation Voltage: NPN BJTs have a low saturation voltage, which means that they can operate at low voltage levels without significant power dissipation.

Conclusion

In conclusion, BiCMOS inverter uses NPN BJTs because of their compatibility with CMOS technology, high gain, high output current, and low saturation voltage. PNP BJTs are not used in BiCMOS inverters because they are not compatible with CMOS technology and have lower gain and output current compared to NPN BJTs.