Gate current requirement for SCR turn-on In typical power SCR applications, the gate current needed to turn on an SCR is of the order of:

Introduction / Context:
The SCR (silicon-controlled rectifier) is a latching device that turns on when properly forward-biased and when a sufficient gate current is applied. Understanding the correct magnitude of gate current avoids overstressing gate drivers and ensures reliable triggering.

Given Data / Assumptions:

• Commercial SCRs often specify gate trigger current Igt in the range of a few milliamps to a few tens of milliamps.
• Anode current capability may be tens to hundreds of amperes, much larger than the gate current.

Concept / Approach:
The gate current only initiates conduction by injecting carriers; it does not have to sustain the load current. Once latched, the SCR continues conducting as long as the anode current exceeds the holding current.

Step-by-Step Solution:
Check relative magnitudes from datasheets: Igt is typically mA, not A.Conclude that “a few mA” is the correct order for gate drive.

Verification / Alternative check:
Application notes recommend gate pulses of a few times Igt for noise immunity, still within mA to tens of mA.

Why Other Options Are Wrong:
Ampere-level or fractions of anode current: Far in excess of what is required and could damage the gate.

Common Pitfalls:
Confusing gate trigger current with holding current or latching current; those are device-specific but still far below anode load currents.

Final Answer:
a few mA