Double tuned amplifierb

A resonant amplifier circuit with two tuned loops is called a double-tuned amplifier circuit , that is, the primary and secondary coils of transformers Ti and T2 are
equipped with parallel resonant capacitors, which have resonance functions. According to different coupling methods, it can be divided into two types: mutual inductance coupling and capacitive coupling, as
shown in Figure 3-20. Figure (a) shows a mutual-inductance coupled double-tuned amplifier, which differs from a single-tuned amplifier in that Ll and C3 tuning circuits are used
to replace the secondary coil . Mutual inductance coupling is used between the Li and the secondary, that is, changing the distance between Li and Li or the position of the magnetic core can
change their coupling degree. Figure (b) shows a capacitively coupled tuned amplifier . The degree of coupling
between the two tuning loops is changed by connecting an external capacitor Ck .