TUNED AMPLIFIERS Simple presentation of Btech students

TUNED AMPLIFIERS Simple presentation of Btech students

1. Tuned Amplifier VBIT DEPARTMENT OF ECE presented by: Name : A. Sai varshith Roll : 22P61A0414

2. . Sometimes an amplifier should be selective. Amplifiers which amplify a specific frequency or narrow band of frequencies are called tuned amplifiers. Mostly used for the amplification of high or radio frequencies.

3. The circuit used for tuning or selecting. Tuning means selecting a specific frequency among a set of frequencies and rejecting all others. Consists of an inductor and a capacitor x L = x c   Fig-01: A tuned circuit

4. According to type of connection to main circuit tuned circuit is of two types. 1. Series tuned circuit: 2. Parallel tuned circuit : Fig-02: A series tuned circuit Fig-03: A parallel tuned circuit

5. Parallel resonance: A parallel circuit containing reactive elements (L & C) is resonant when the circuit power factor is unity i.e.applied voltage and the supply current are in phase . Resonant frequency: the frequency at which parallel resonance occurs is called the resonant frequency fr . fr =  

6. 1.Impedance of tuned circuit: at resonance, l is minimum, Zr is maximum . It is clear from Fig.04 that Zr decreases for the values above and below the fr.Hence the selection of a particular frequency and rejection of other frequencies is possible . z r = L /CR Fig-04:

7. 2.Circuit current: Line current I =V/ Zr Since Zr is very high the line current is minimum at resonance condition. 3.Quality factor: The ratio of inductive reactance of the coil at resonance to its resistance is known as quality factor. Denoted by,  

8. Small power loss. High selectivity . Smaller Collector supply voltage .

9. The figure below details the bandwidth and frequency response of the tuned amplifier . Fig-05:

10. It consists of a transistor amplifier and a tuned circuit, output can be obtained by- I) a coupling capacitor Ii) a secondary coil Fig-06: A coupling capacitor Fig-07: A secondary coil

11. It consists of a single transistor amplifier and two tuned circuits one is L1C1 in the collector and other is L2C2 at the output . Fig-08: A double tuned Amplifire

12. Large output at L 1 C 1 Output in L 2 C 2 High frequency signal fr =fin

13. The frequency response of double tuned circuit depends on the degree of coupling between two coils . Two types of coupling: i ) loose coupling ii) tight coupling Fig-09:

14. There are two reasons which is given below: 1.Low frequencies are never single. 2.High values of L & C.