Electronics 1

The University of Toledo hwbivtc - 1 EECS:3400 Electronics I Dr. Anthony D. Johnson

Homework Assignment #12

BJT Inverter VTC

Electrical model of a bipolar transistor inverter circuits is shown in Figure 1.

Figure 1 BJT inverter circuit.

RC

RB vI

vO

VCC

VBEtrsh

{

VBEon

vBE

iB

0

Properties of the circuit will be calculated using the following circuit parameter values:

a) whole IC

- substrate doping NAs = 6x10 20 acceptor. atoms/m3

- epitaxial layer doping NDe = 5x10 21 donor atoms/m3

- base-diffusion doping NAb = 10 23 acceptor atoms/m3

- n+ emiter-diffusion doping NDe = 10 24 donor atoms/m3

- power supply VCC = 5V - diel. const. of vacuum εo= 8.85.10 -12 F/m

- electron mobility µn= 0.06 m 2/Vs, - diel. const. of Si εSi =11.7 εo

- hole mobility µp= 0.038 m 2/Vs, - diel. const. of SiO2 εox=3.97 εo

b) transistor

- IS= 10 -16A - rb= 0

- βF= 70 - re= 0 - βR= 1 - rc= 5.5 - τF= 0.3ns - τS= 25ns - Cjeo= 0.4pF - Cjco= 0.25pF - φe= 0.9V - φc= 0.7V - me= 0.5 - mc= 0.33

The University of Toledo hwbivtc - 2 EECS:3400 Electronics I Dr. Anthony D. Johnson Student Name _______________________________________

- VBEtrsh= 0.5V - VBEon= 0.6V - VBEsat= 0.8V - VCEsat= 0.1V

c) linear circuit elements - base resistor RB = 14 kΩ - collector resistor RC = 1.1kΩ - power supply VCC = 5V

Homework Assignment:

Analyze the inverter circuit and determine I/O voltage pairs at four characteristic points on the inverter’s VTC:

(a) (0,VOH) (c) (VIL,V02)

(b) (VCC,VOL) (d) (VIH,V01).

under two different conditions: 1) inverter output is not loaded, as shown in Figure1, 2) inputs of two, or more, identical inverters are connected to the inverter’s output , as shown

in Figure 2.

Do the analysis and design described under 5.1 and 5.2 below.

Vcc

RC

vO

vI

RC

RB

RB

RB

RC Q1

Q3

Q2

Figure 2 BJT inverter circuit loaded by two identical inverter circuits.

Show the following steps of the solution process.

1. Characteristic points on the VTC under no load condition

The University of Toledo hwbivtc - 3 EECS:3400 Electronics I Dr. Anthony D. Johnson Student Name _______________________________________

1.1 Characteristic point (vI,v0) = (0,VOH)

1.2 Characteristic point (vI,v0) = (VCC,VOL)

1.3 Characteristic point (vI,v0) = (VIL,V02)

1.4 Characteristic point (vI,vO) = (VIH,V01)

2. Characteristic points on the VTC of a loaded inverter

3. Noise margins, logic swing and transition region

4. Maximum Fan-out

5. Design problems 5.1 Given the BJT inverter circuit of Figure 1, and given the required noise margin NMH0 = 1.3V,

determine whether the inverter circuit can drive successfully twelve inverter inputs in parallel.

5.2 Given a BJT inverter circuit of Figure 1, and given the required noise margin value, NMH0 = 0.9V, determine the value of RC, so that the circuit satisfies the requirement on the noise margine.