Why is there a power supply at both ends of the triode? This is a part of the car controller circuit. Does it require so many power supplies of different values?
Maxwell Posted on August 3, 2020
The first picture is very simple. U3-21 is the control terminal. When the output is high, both transistors are turned on. The electricity of VC is actually the voltage of VB through the transistor Q20 and resistor R70.
The second picture is similar to the first picture, and at the same time increases the VF output current capability;
The third picture did not understand
Vanessa Posted on August 3, 2020
When VF is short-circuited or over-current, causing the current flowing through R79 (3.9R) to be greater than 180mA, VR79 = -Vbe> 3.9 * 0.18 = 0.7 (V), Q23 is saturated and turned on. Note that the c pole of Q23 and the pole of Q24 The b pole is connected. As a result, the Vbe of Q24 is clamped to less than 0.5V by the saturation voltage drop Vsat of Q23, Q24 is cut off, and the short-circuit current is disconnected.
Angelina Posted on August 3, 2020
One input and one output of the two power supplies are controlled by a triode, which is equivalent to an electronic switch.
