Thursday, October 2, 2014
Simple Wideband RF Amplifier Circuit
- The feedback circuit is formed by RF transformer Tri. The input and output impedance of the preamplifier is 509 for optimum perform- ance. Network Rs-Cs may have to be added to preclude oscillation outside the pass-band, which ranges from about 100 kHz to 50 MHz.
- This circuit is of the second kind, using an RF power transistor as the active element.
- Feedback is also required to ensure correct termination . (50 Q) of the aerial, since bipolar transistors normally exhibit a low input impedance.
- The input winding is l turn, the out- put winding 5 turns with a tap at 3 turns. is formed by RF transformer Tri. The input and output impedance of the preamplifier is 509 for optimum performance.
- Network Rs-Cs may have to be added to preclude oscillation outside the pass-band, which ranges from about 100 kHz to 50 MHz. The gain is approximately 9.5 dB, the noise figure is between 2 and 3 dB, V and the third-order output intercept point is at least 50 dBm. The input/output transformer is wound on a Type FT37-75 fer- rite core from Micrometals. The input winding is l turn, the output winding 5 turns with a tap at 3 turns.
- Also, the noise figure is not increased because virtually no signal is lost. The common base amplifier is based on a UHF class A power Q transistor Type 2N5lO9 from Motorola.
- The gain is approximately 9.5 dB, the noise figure is between 2 and 3 dB, V and the third-order output intercept point is at least 50 dBm. The input/output transformer is wound on a Type FT37-75 ferrite core from Micrometals.
- A linear RF amplifier can be made in two ways: (l) with the aid of a linear active element, or (2) with a non-linear element operating with negative feed- back.
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