15 Questions
What is the primary difference between a Power BJT and a signal BJT?
Voltage and current ratings
What is the region in which the collector current is almost zero?
Cutoff region
What is the purpose of connecting a diode in series with the collector?
To block negative collector-emitter voltages
What is the consequence of high power loss during turn-on or turn-off?
Local hot spots and damage
What is the characteristic of a Power BJT that makes it a current-controlled device?
Low current gain
What is the primary requirement for a Power BJT to emulate an ideal switch?
High base current
What is the term used to describe the maximum voltage between collector and emitter in the cutoff region?
VCEO
What is the primary advantage of Power BJTs over other devices?
Full control over the output
What is a significant difference between Power BJT and signal BJT?
Voltage and current ratings
Power BJTs can block negative collector-emitter voltages.
False
What happens when both the collector-emitter voltage and the collector current are high?
Second breakdown occurs, leading to high power loss and local hot spots.
The operation of a Power BJT is controlled by its ______________ gain.
low current
Match the following characteristics of Power BJTs:
Low current gain = Compared to signal amplifiers High power loss = During turn-on or turn-off Current-controlled device = Characteristics of Power BJT Ideal switch = Emulated by Power BJT in on-state
Power BJTs have been completely replaced by other devices.
True
What is the primary requirement for a Power BJT to operate in the on-state?
High base current
Study Notes
Power BJT: Bipolar Junction Transistor
- First SCSD (Self-Controlled Switching Device) that allows full control
- Many other devices classified as "Transistors" have been developed, almost replacing BJTs
Construction and Operating Characteristics
- Power BJT differs significantly from signal BJT due to voltage and current ratings requirements
- In the cutoff region, base current (iB) ≤ 0 and collector current is almost zero
- Maximum voltage between collector and emitter under this condition is denoted by VCEO (the rated voltage)
Emulating an Ideal Switch
- High base current in the on-state is required for the operating point to lie on the hard saturation line
- Associated with the lowest voltage drop across the device
Voltage Blocking
- BJTs cannot block negative collector–emitter voltages
- A diode connected in series with the collector is required to block negative voltage
Second Breakdown
- Occurs when both collector–emitter voltage and collector current are high, during turn on or turn-off
- Results in high power loss, local hot spots appear in the semiconductor
- Current density increases in hot spots, leading to damage
BJT Characteristics
- Current-Controlled Device
- Low current gain compared to signal amplifiers (around 10)
Power BJT: Bipolar Junction Transistor
- First SCSD (Self-Controlled Switching Device) that allows full control
- Many other devices classified as "Transistors" have been developed, almost replacing BJTs
Construction and Operating Characteristics
- Power BJT differs significantly from signal BJT due to voltage and current ratings requirements
- In the cutoff region, base current (iB) ≤ 0 and collector current is almost zero
- Maximum voltage between collector and emitter under this condition is denoted by VCEO (the rated voltage)
Emulating an Ideal Switch
- High base current in the on-state is required for the operating point to lie on the hard saturation line
- Associated with the lowest voltage drop across the device
Voltage Blocking
- BJTs cannot block negative collector–emitter voltages
- A diode connected in series with the collector is required to block negative voltage
Second Breakdown
- Occurs when both collector–emitter voltage and collector current are high, during turn on or turn-off
- Results in high power loss, local hot spots appear in the semiconductor
- Current density increases in hot spots, leading to damage
BJT Characteristics
- Current-Controlled Device
- Low current gain compared to signal amplifiers (around 10)
Learn about the construction and operating characteristics of Power BJTs, including their differences from signal BJTs and their voltage and current ratings. Understand the cutoff region and maximum voltage between collector and emitter.
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