### BJT Transistor hFE Test Fixture

Circuit Description:

The text fixture above measures the ratio of collector current (Ic) to base current (Ib) of bipolar transistors. A 3 position switch selects one of 3 base current conditions, 1mA, 0.5mA and 0.025mA. Collector current is measured with a DMM connected across points A and B, and the hFE or gain factor is determined by multiplying the DMM current reading by a factor of 1, 2, or 4 depending on the switch setting. For example, when the switch is in the X1 position, the base current will be about 1mA and so the hFE value will be the DMM reading directly. When the switch is in the X2 position, the base current will be half a much, so the DMM reading is multiplied by 2, or 4 if the switch in the 4X position. The supply voltage should be close to 9 volts for fairly accurate measurements. Also, the transistor should be removed from the fixture after each test to avoid excessive battery drain.

```
Transistor   Multiplier     Collector     Collector      hFE
Voltage     Current (mA)

2N2219A        X1            2            125            125
NPN            X1            0.2          84              84
X2            5.5          65             130
X2            0.2          46              92
X4            6.6          30             120
X4            0.2          26             104

2N2222A        X1            1.1          153            153
NPN            X1            0.2          98              98
X2            3            113            226
X2            0.2          64             128
X4            5.4          67             268
X4            0.2          41             164

2N3906         X1            2.9          101            101
PNP            X1            0.2           43             43
X2            5             65            130
X2            0.2           28             56
X4            6.6           34            136
X4            0.2           18             72

2N3904         X1            3.4           94             94
NPN            X1            0.2           34             34
X2            4.8           65            130
X2            0.2           21             42
X4            6.2           39            156
X4            0.2           13             52

2N3053         X1            1.5          130            130
NPN            X1            0.2           71             71
X2            4.5           69            138
X2            0.2           38             76
X4            6.4           34            136
X4            0.2           19             76

2SA1015        X1            2.2           119           119
PNP            X1            0.2            50            50
X2            4              80           160
X2            0.2            35            70
X4            5.6            49           196
X4            0.2            26           104

2N4123         X1            3.9            82            82
NPN            X1            0.2            46            46
X2            5.1            59           118
X2            0.2            30            60
X4            6.4            34           136
X4            0.2            18            72

```