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Correct answer: emitter of a pnp transistor

The symbol shown is a bipolar junction transistor (BJT). The arrow identifies the emitter, and the direction of the arrow indicates the transistor type:

• an arrow pointing toward the base means a pnp transistor
• an arrow pointing away from the base means an npn transistor

In the diagram, terminal 1 is the lead with the arrow pointing inward toward the base, so it is the emitter of a pnp transistor.

• collector of a pnp transistor is incorrect because the collector does not have an arrow.
• gate of a junction FET is incorrect because this symbol is a BJT, not a FET.
• source of a MOSFET is also incorrect because MOSFET symbols use a different gate and channel structure.

Therefore, terminal 1 represents the emitter of a pnp transistor.

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Correct answer: gate of an n-channel junction FET

The symbol shown is for a junction field-effect transistor (JFET). In this symbol:

• The vertical line represents the channel between the drain and source.
• The terminal with the arrow pointing toward the channel is the gate.

For an n-channel JFET, the arrow on the gate points toward the channel, indicating the direction of conventional current in the p–n junction.

• A drain terminal does not have an arrow in this manner.
• Bipolar transistors use base, collector, and emitter terminals with a different symbol.
• A pnp transistor symbol is distinctly different from a JFET.

Therefore, terminal 2 represents the gate of an n-channel junction FET.

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Correct answer: drain of an n-channel junction FET

The symbol shown is a junction FET (JFET). The arrow on the gate points toward the channel, which identifies it as an n-channel JFET.

In standard JFET symbols:

• the left terminal is the gate
• the top terminal is the drain
• the bottom terminal is the source

Since label 3 is connected to the top terminal, it represents the drain of an n-channel JFET.

• source of an n-channel junction FET is incorrect because the source is the lower terminal in this symbol.
• gate of a p-channel junction FET is incorrect because the arrow direction indicates an n-channel device, and the gate is the left terminal.
• emitter of a pnp transistor is incorrect because this symbol is a FET, not a bipolar transistor.

Therefore, terminal 3 is the drain of an n-channel junction FET.

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Correct answer: gate of a MOSFET

The symbol shown is for a MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

In this symbol:

• Terminal 2 is the insulated gate, which controls current flow.

• Terminals 1 and 4 are the source and drain, forming the conduction path.

• Terminal 3 is the substrate (body) connection.

• A bipolar transistor uses base, collector, and emitter terminals.

• A silicon controlled rectifier has anode, cathode, and gate terminals with a different symbol.

• A dual diode would show two diode junctions.

Therefore, terminal 2 represents the gate of a MOSFET.

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Correct answer: grid of a tetrode

The symbol shown is for a tetrode valve, which has:

• a filament (heater)
• a control grid
• a screen grid
• an anode (plate)

In the diagram, terminal 3 connects to one of the grid structures positioned between the filament and the anode.

• The filament is the heater element at the bottom of the valve.
• The anode is the plate located at the top.
• A pentode would show an additional grid.

Therefore, terminal 3 represents the grid of a tetrode.

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Correct answer: screen grid of a tetrode

The symbol shown is for a tetrode valve, which contains:

• Filament (heater) – heats the cathode
• Cathode – emits electrons when heated
• Control grid – controls electron flow from cathode to anode
• Screen grid – reduces capacitance between control grid and anode
• Anode (plate) – collects electrons to produce current flow

In the diagram:

• Terminal 1 is the heater (filament)

• Terminal 2 is the cathode

• Terminal 3 is the control grid

• Terminal 4 is the anode

• Terminal 5 is the screen grid

• The heater is at the bottom of the symbol.

• A triode would have only one grid.

Therefore, terminal 5 represents the screen grid of a tetrode.

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