Contents
- 1 What is high frequency model of transistor?
- 2 What is the frequency of a transistor?
- 3 Can current flow backwards through a transistor?
- 4 Why does voltage gain at high frequency?
- 5 How are high frequency transistors used in the real world?
- 6 What kind of transistors are used in CATV amplifier?
- 7 How is the Miller theorem used in high frequency circuits?
What is high frequency model of transistor?
When input signal to an amplifier is in the range of ten to hundred Kilo Hertz, a small signal-low frequency model of the transistor can be used for analysis. But as the frequency increases, internal capacitance of the transistor will strongly effect it’s performance.
What is the frequency of a transistor?
By definition, fαe is the frequency at which hfe (beta, the common emitter of ac short–circuit current gain), has decreased 3 dB below hfeo (the value of hfe at 1 kHz). A typical curve of hfe versus frequency for a transistor with an fαe of 100 kHz is shown in Figure 2.
Why the gain of a transistor amplifier falls at high frequency?
The gain of the transistors falls at higher frequency due to the parasitic capacitance.
Can current flow backwards through a transistor?
Yes current can flow in both directions. An NPN transistor backwards is also an NPN. There will still be a reverse beta, however, the backwards NPN transistor won’t work as well as a correctly oriented one will.
Why does voltage gain at high frequency?
The gain falls at high frequency and low frequency: The low input impedance offered by the capacitor {C} present in the circuit and also the transistor gain reduces the output at high frequency are the reason off gain falling down at high frequencies.
What is the reason for fall in gain at higher frequencies?
How are high frequency transistors used in the real world?
High Frequency (RF) Transistors are transistors that are used for small signals that run at high frequencies for high-speed switching applications. These are transistors that are used for high frequency signals and must be able to switch on and off at very high speeds. High frequency transistors are used in HF, VHF, UHF, CATV, and MATV
What kind of transistors are used in CATV amplifier?
High frequency transistors are used in HF, VHF, UHF, CATV, and MATV amplifier and oscillator applications. They have a maximum frequency rating of about 2000 MHz and maximum Ic currents from 10 to 600mA. They are available in both npn and pnp forms.
What is the maximum frequency of a PNP transistor?
They have a maximum frequency rating of about 2000 MHz and maximum Ic currents from 10 to 600mA. They are available in both npn and pnp forms.
How is the Miller theorem used in high frequency circuits?
The Miller Theorem is very useful in the development of high frequency equivalent transistor circuits. This theorem allows us to transform a series capacitance into equivalent shunt (parallel) capacitances that are much larger than the original capacitance value.