Transistor Signals

Transistor Final Stage Function












The transistor takes on a number of applications that must be understood to effectively analyze a circuit.

The transistor in operation functions as two parts much like a relay. Both the relay and the transistor control high currents with a low current signal.

The base/emitter path functions as the control circuit activated by the control module to over- see or control the work.

The collector/emitter path functions as the work side of the circuit, supplying power or switching on the work.

In operation the transistor can be switched ON momentarily, or supply a constant power or ground.

The transistor can also be modulated or pulsed to supply a modulated square wave signal.

Modulated, Momentary, Constant B- as Input/Output







The input signal of control module 1 is an out put signal of control module 2.
Control module 2 through activation of its internal transistor provides a ground input for control module 1.

The input signal at control module 1 is either a momentary/constant signal (i.e torque convertor signal from TOM to DME) or a modulated signal (i.e. vehicle speed signal ASC to DME).







Typical Application of Modulated, Momentary, Constant B- as Input/Output Signal

- A/C KO Signal
- Speed Signal From ABS/ASC
- TI/TD Output Signal From DME

Momentary/Constant B+ as an Input/Output Signal







The input of control module 2 is controlled by control module 1 through internal activation of the transistor. Control module 1 provides power for the input circuit of control module 2.

Typical Application of Momentary/Constant B+ as an Input/Output Signal

- OBC Code Signal to DME
- A/C Signal to DME

Constant B-/B+ To Energize a Component

Constant B-







Output function to energize a component.

Relay is energized by control module. Internal activation of the transistor provides a ground for the relay coil.

Constant B+







Control module output function to energize a component.

Transistor controls output function of the control module.
Control module supplies power to the relay. The relay is activated by the control module through internal activation of the transistor which provides a ground for the relay coil.

Modulated B-/B+ To Operate A Component

Modulated B-







Output function to operate a component.

The idle valve motor is operated by the control module through internal activation of the transistor which provides a ground for the open winding of the valve.

The idle control valve is operated by regulation of the duty cycle at a specific frequency.

Typical Application of modulated B-

- Idle Control Motor
- Purge Valve
- Injector
- Ignition Coil

Modulated B+







Output function to operate a component.

The motor is controlled by a transistorized function of the control module, which provides a modulated voltage at a specific frequency to the motor. The throttle position is changed by altering the Duty Cycle of the pulses.