In this circuit of a 1975 publication, a silicon transistor is used as a sensor. We can employ a BC548. R1 and R2 are of the order of 10 k, chosen to obtain a voltage approximately half of the supply in B. R5 is of the order of 10k and R3, R4 is a divider with equal resistors from 10k to 47k. The supply can be made with voltages from 6 to 12 V. The load must be a 2k2 resistor.
| Clique na imagem para ampliar |
