# How do I test a bipolar transistor for Collector-Emitter Saturation Voltage on my curve tracer?

### 问题：

How do I test a bipolar transistor for Collector-Emitter Saturation Voltage on my curve tracer?

### 答案：

Collector-Emitter Saturation Voltage - VCE(sat)

What It Is:

Collector-emitter saturation voltage is the VC below which an increase in IB does not cause an increase in IC.  The measurement is taken with specified values of IC and IB.

On the curve tracer, VC is applied by the Collector Supply.  Forward bias is applied by the Step Generator, and IC is sensed at the collector terminal.

What The Display Shows:

The display shows VC on the horizontal axis, and the resulting IC on the vertical axis.  With base drive applied, the curve will initially rise as IC is a function of VC.  The curve will then flatten out as the base drive assumes control.

The specification is met when, at the specified base drive and IC, VC at the “knee” of the curve is less than or equal to the specified maximum.

How To Do It:

1. Set controls:

A: Max Peak Volts to the lowest setting above the specified VC

B: Max Peak Power Watts to the lowest range that will satisfy (IC x VC)

C: Horizontal Volts/Div to display specified VC between the 5th and 10th horizontal divisions

D: Vertical Current/Div to display the specified IC between the 5th and 10th vertical divisions

E: Collector Supply Polarity to (+DC) for NPN or (-DC) for PNP

F: Configuration to (Base/Step Gen, Emitter/Common)

G: Step Generator to Current

H: Number Of Steps to zero

I: Offset/Step Amplitude to one increment below the specified base drive

J: Variable Collector Supply to minimum % (full ccw)

K: Dot Cursor ON
2. Apply power to the transistor:

A: Position the Left/Right switch as appropriate

B: Press Offset Aid until the specified IB is applied

C: Slowly increase the Variable Collector Supply % until the specified IC is reached

3. Compare to data sheet specifications:

Check that at the specified IC, VC is less than or equal to the specified maximum.