transistor defects Flashcards
(11 cards)
Short circuit between collector and emitter: what is the effect
Shorting the emitter and collector of a transistor can result in a loss of functionality as a switch. The transistor will behave more like a diode, allowing current to pass in the forward bias direction and blocking it in the reverse bias condition. The actual voltage levels will depend on the specific circuit’s biasing, according to a forum for electronics discussion.
Open circuit between collector and emitter
When the transistor is in the cutoff or “off” state, the collector and emitter act as an open circuit, and there is no current flow between them, The collector voltage would typically be pulled up towards the power supply (Vcc) through any collector resistor present in the circuit.
Short circuit between base and emitter
If the base and emitter are shorted, the transistor will be in a cutoff state because no current can flow from the base to the emitter to initiate conduction. This means that the collector current will be zero.
Open circuit between base and emitter:
When the base-emitter junction is open, there is no path for base current to flow. This will put the transistor in cutoff mode, meaning no collector current flows, and the collector voltage (Vc) will be equal to the power supply voltage (Vcc), according to an article from Vaia.
Identifying an open inductor
creates an open circuit or infinite resistance. This interruption in the circuit prevents current flow through the component. In short, a multimeter indicating extremely high or infinite resistance across the inductor, or visible signs of damage, are the primary indicators of an open inductor.
ways to indicate or recognize a shorted inductor
Decreased Inductance: If a short circuit occurs within the inductor’s windings, the overall inductance of the component will decrease, This change in inductance might be detected by measuring the inductor’s inductance using an LCR meter.
how is an open resistor typically indicated:
Infinite Resistance: When measured with an ohmmeter (a function on a multimeter), an open resistor will display a very high resistance value, often indicating infinity or “OL” (Overload).
No Current Flow: If the resistor is part of a series circuit, an open resistor will stop the flow of current entirely. In a parallel circuit, only the branch containing the open resistor will lose current flow.
Circuit Malfunction: If the circuit relies on the resistor for a specific function, an open resistor will cause that function to fail. For example, in a circuit with a light bulb, an open resistor in series with the bulb would prevent it from lighting up.
Visual Signs: While not always present, sometimes an open resistor can show visible signs of damage, such as charring, cracking, or discoloration, particularly if the failure was caused by overheating,.
resistors that are shorted. how is this indicated
A shorted resistor is indicated by a very low or zero resistance reading on a multimeter when measuring across its terminals. Ideally, a resistor will have a resistance value within its specified tolerance range, but a shorted resistor will show a resistance close to zero ohms, indicating a direct connection bypassing the intended resistance.
Identifying an “open” diode
An “open” diode is a faulty diode that acts like an open circuit and prevents current from flowing in either direction.
In summary, if your multimeter shows an “OL” reading in both the forward and reverse bias tests (when in diode test mode), or an infinite resistance in both directions (when in resistance mode), it’s a strong indication that the diode is open and needs to be replaced.
diodes that are shorted. how is this indicated
When a diode fails in a shorted condition, it loses its ability to block current in the reverse direction and acts like a simple conductor.
Multimeter Reading (Diode Test Mode): A good diode will display a voltage drop (typically 0.5V - 0.8V for silicon diodes) in the forward direction and an open circuit (indicated as “OL” or 1) in the reverse direction. A shorted diode, however, will show a very low voltage drop (close to zero volts) or the same voltage drop reading in both forward and reverse directions.
