<P> A double - tuned amplifier is a tuned amplifier with transformer coupling between the amplifier stages in which the inductances of both the primary and secondary windings are tuned separately with a capacitor across each . The scheme results in a wider bandwidth and steeper skirts than a single tuned circuit would achieve . </P> <P> There is a critical value of transformer coupling coefficient at which the frequency response of the amplifier is maximally flat in the passband and the gain is maximum at the resonant frequency . Designs frequently use a coupling greater than this (over-coupling) in order to achieve an even wider bandwidth at the expense of a small loss of gain in the centre of the passband . </P>

Effect of cascading double tuned amplifier on bandwidth