Transistor Symbols: NPN, PNP, MOSFET, JFET & IGBT in One Chart

A transistor symbol shows three terminals and one arrow. In a bipolar junction transistor (BJT), the arrow is on the emitter: it points out for NPN and in for PNP. In a MOSFET, the arrow sits on the channel and points in for N-channel and out for P-channel. Letters tell you the pins: B, C, E for a BJT, and G, D, S for a FET.

This guide puts the common transistor symbols in one chart, then explains how to tell them apart, how to read the pins on a schematic, and what to check before the symbol becomes a footprint on your PCB.

Transistor Symbols at a Glance

Transistor type	What to look for in the symbol	Pins	Typical designator
NPN BJT	Circle optional; emitter arrow points out	Base, Collector, Emitter	Q
PNP BJT	Emitter arrow points in	Base, Collector, Emitter	Q
N-channel MOSFET	Gate plate, broken channel, arrow points toward the channel	Gate, Drain, Source	Q
P-channel MOSFET	Same, but the arrow points away from the channel	Gate, Drain, Source	Q
N-channel JFET	Solid channel, gate arrow points in	Gate, Drain, Source	Q
P-channel JFET	Solid channel, gate arrow points out	Gate, Drain, Source	Q
IGBT	MOS-style gate with a BJT-style collector and emitter	Gate, Collector, Emitter	Q

Most libraries use Q for transistors, including MOSFETs and IGBTs. Some use T or TR, so follow your own library or your customer's standard.

BJT Symbols: NPN and PNP

The BJT symbol has a vertical bar for the base region. The base wire joins the bar from one side. The collector and emitter lines leave the bar at an angle, and the emitter line carries the arrow.

• NPN: the arrow points away from the base. A common memory aid is "Not Pointing iN".
• PNP: the arrow points toward the base.

The arrow shows the direction of conventional current in the emitter. An NPN transistor switches on when the base is driven higher than the emitter, and a PNP when it is driven lower. For a closer look at how they differ, read the difference between PNP and NPN transistors, and for bias circuits see transistor biasing and amplifier design.

The circle around the symbol is optional. IEC style drawings usually show it, and many ANSI style drawings leave it out. Both mean the same part.

MOSFET Symbols: N-Channel and P-Channel

A MOSFET symbol has a gate plate that is separated from the channel by a gap, to show the insulated gate. The channel is drawn as three short segments for an enhancement-mode device, which is off at zero gate voltage. A depletion-mode MOSFET uses one solid channel line, because it conducts at zero gate voltage.

• N-channel: the arrow on the middle segment points toward the channel.
• P-channel: the arrow points away from the channel.
• Body diode: many symbols add a diode between source and drain. It is part of the device, and it shows which way the body diode conducts.

In most low-side switch circuits the source goes to ground and the drain goes to the load. See how a MOSFET works for the working principle and the IRFZ44N guide for a common example.

JFET Symbols

A JFET symbol has a solid channel line and a gate arrow. The arrow points into the channel for N-channel and out of it for P-channel. A JFET conducts at zero gate voltage, so it is normally on. For the basics of field-effect devices, see what a field-effect transistor is.

IGBT Symbol

An IGBT is drawn with a MOS-style gate on the left and a BJT-style collector and emitter on the right. It is used in higher-voltage power switching such as motor drives and inverters. Its pins are gate, collector and emitter.

Darlington Pair Symbol

A Darlington pair is drawn as two transistors joined together, with the emitter of the first feeding the base of the second. The pair behaves like one transistor with high current gain. See a high-current motor driver using Darlington pair transistors for an example.

How to Read Transistor Pins on a Schematic

• BJT: the wire touching the bar is the base. The line with the arrow is the emitter. The other line is the collector.
• MOSFET: the wire facing the gap-separated plate is the gate. The terminal connected to the arrow side is the source. The remaining one is the drain.
• Check the label: the schematic often prints B, C, E or G, D, S next to the pins, and the part number tells you which package pinout applies.

The symbol shows function, not pin position. The same transistor in a different package can have its pins in a different order, so always check the datasheet pinout. See transistor pinout and the BC547 guide for examples.

Common Mistakes With Transistor Symbols

• Mixing up NPN and PNP. Check the emitter arrow direction before you wire the supply.
• Assuming symbol pin order equals package pin order. Map each symbol pin to the footprint pad by name, not by position.
• Swapping drain and source on a MOSFET. The body diode then conducts the wrong way.
• Using a generic symbol for a specific part. Use a symbol that has the correct pin names for the part you buy.
• Forgetting enhancement or depletion mode. The channel line style tells you which one it is.

Related symbols are covered in our guides to diode symbols, resistor symbols and capacitor symbols. For the full set, see PCB schematic symbols and electronic component symbols.

Transistor Symbols FAQ

How do I tell NPN from PNP in a schematic?

Look at the emitter arrow. It points out for NPN and in for PNP.

What is the symbol for a MOSFET?

A gate plate separated from a channel by a gap, with drain and source terminals. The channel arrow points in for N-channel and out for P-channel.

What do B, C and E mean on a transistor?

Base, collector and emitter, the three pins of a bipolar transistor.

What do G, D and S mean?

Gate, drain and source, the three pins of a FET.

What is the difference between enhancement and depletion MOSFET symbols?

An enhancement-mode MOSFET has a broken channel line. A depletion-mode MOSFET has a solid channel line.

Is the circle around a transistor symbol required?

No. It is optional and the part is the same with or without it.

Conclusion

To read any transistor symbol, find the arrow first, then check which way it points and which terminal it sits on. Then confirm the pin names against the datasheet before you build the footprint.

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