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Tip STATUS: Correct working proto

B900 is a simple trough hole discrete power supply with good performance. The regulator circuit make use of only six transistors. Although one set of 2N3055/BD139 can handle the 8A, I use two sets of them to get a higher amplification factor. The BC547 and BD140 are the one’s with the highest hFE classification.

Table 1. Typical electrical characteristics B900 compared with L7805
Symbol Parameter Test conditions B900 L7805 Unit

Imax

Maximum current

?°C

8

1

A

Vo

Output voltage

Imax 25°C

3.46

5

V

ΔVo

Line regulation

Imax 25°C

6

0.4

mv/V

ΔVo

Load regulation

Imax 25°C

12

16

mv/A

SVR

Supply voltage rejection

50Hz

68

68

dB

Vd

Dropout voltage

Imax 25°C

2

2

V

ΔVo/ΔT

Output voltage drift

-0.5

-1.1

mV/ΔC
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Figure 1. Schematic diagram B900