3-25
Figure 3-23.—Comparison of SCR and TRIAC symbols.
Figure 3-24.—Back to back SCR equivalent circuit.
The difference in current control between the SCR and the TRIAC can be seen by comparing their
operation in the basic circuit shown in figure 3-25.
In the circuit shown in view A, the SCR is connected in the familiar half-wave arrangement. Current
will flow through the load resistor (RL) for one alternation of each input cycle. Diode CR1 is necessary to
ensure a positive trigger voltage.
