Bicmos Inverter

 BICMOS INVERTER:-

A simple BiCMOS inverter can be constructed from a pair of MOS transistor and NPN transistors. Each of the MOS transitors are cascaded with an NPN transistor. When the input is HIGH, the NMOS transitor is conducting becoming the base current for the Q2 NPN transistor causing the discharge current to drop. Conversely when the input is LOW, the PMOS transistor is conducting becoming the base current for the Q1 NPN transistor, causing the output the increase.

The inverter has low input impedance and low output impedance. The inverter has high current driving capability, occupies smaller area and has high noise margins. Output voltage swing should be reduced for a better performance of BiCMOS circuit.

                                                                      fig1-Bicmos Inverter Circuit

A BICMOS inverter circuit comprising:

1) An input for receiving a high or low signal;

a first P type MOS transistor having a gate connected to said input, a source adapted to be connected to the positive terminal of a voltage source, and a drain connected to a signal output node.

2) A first N type MOS transistor having a gate connected to said input, a source adapted to be connected to the negative terminal of said voltage source, and a drain connected to said signal output node.

3) A first bipolar transistor having an emitter, a base connected to said signal output node, and a collector connected to the source of said first P type MOS transistor.

4) A second bipolar transistor having a base connected to the base of said first bipolar transistor, an emitter connected to the emitter of said first bipolar transistor, and a collector connected to the source of said first N type MOS transistor.

5) A second P type MOS transistor having a gate connected to said input, a source connected to the source of said first P type MOS transistor, and a drain connected to the emitter of said first bipolar transistor.

6) A second N type MOS transistor having a gate connected to said input, a source connected to the source of said first N type MOS transistor, and a drain connected to the emitter of said first bipolar transistor.

7) A logic gate output connected to the emitter of said first bipolar transistor.

Features of BiCMOS Gate:-

1.This has the advantages of both the BJTs and CMOS gates.

2.The power driver (BJT amplifier) in the output stage is capable of driving large loads.

3.The circuit, because of its CMOS input transistors, has high input impedance.

4.The output impedance of the circuit is low.

5.The noise margin is high because of the CMOS input stage.

6.The supply voltage VDD is 5 V.

7.The chip area is small.

References:-

A. R. Alvarez and D. Schucker, "BiCMOS Technology for Semi-Custom Integrated Circuits", Cust. Int. Cir. Conf., pp. 22.1.1-22.1.5, 1988.

A. Bellaovar and S. H. K. Embabi, "Scaling of Digital BiCMOS Circuits", 1989 Int. Electron Devices Meeting, pp. 572-575.

Author: Ayush Patidar