72. PNP Transistor for Sensor Module Power Control

In a battery-powered IoT device, turning OFF unused peripherals during sleep mode can dramatically extend battery life. A PNP transistor as a high-side switch on the 5V rail lets the MCU completely disconnect power to the sensor module.

When the MCU drives the PNP base LOW (through a resistor), current flows from emitter to base, turning the transistor ON and supplying 5V to the sensor. When the base is HIGH, the transistor turns OFF and the sensor draws zero current.

A PNP is used (instead of NPN) because it switches on the high side — between the 5V supply and the load. The emitter connects to 5V, and the collector feeds the sensor module.

Required: PNP · Ic ≥200mA · Vceo ≥20V · hFE ≥80 · Vce(sat) ≤400mV · ≥200mW · SOT-23 · SMD

Go to DigiKey.com → Discrete Semiconductor Products → Transistors - Bipolar (BJT) - Single

Apply these filters:

• Transistor Type → PNP
• Current - Collector (Ic) (Max) → 200mA or higher
• Voltage - Collector Emitter Breakdown (Max) → 20V or higher
• DC Current Gain (hFE) (Min) → 80 or higher
• Vce Saturation (Max) → 400mV or lower
• Package / Case → SOT-23-3 (TO-236)
• Part Status → Active

Tip: For battery-powered designs, check the transistor’s base-emitter leakage current. Even when OFF, a small leakage current flows. For most SOT-23 PNP transistors this is negligible (nanoamps), but verify in the datasheet if ultra-low power matters.

The filtered list will show matching parts. Before you pick one, check: Is it Active? Is stock available? Is the manufacturer reputable? Is a datasheet available?

Full checklist: How to Select a Safe, Production-Ready Component — EWskills Guide

➡ View Matching Parts — PNP, SOT-23, Ic≥200mA, Vceo≥20V, hFE≥80