RC oscillators with oscillation frequency independent of the op.-amp. gain-bandwidth product
Andrzej Borys, Ryszard Wojtyna · International Journal of Electronics · 1993
Applying the determining equation proposed by Chua and Tang (1982), a frequency sensitivity problem in RC op.-amp. based oscillators is considered. A new expression for the sensitivity of oscillation frequency, ωo, to changes in any oscillator parameter is developed. Then, the condition for this frequency to be insensitive to changes in the gain-bandwidth products (GB) of the op.-amp. used in the oscillator is formulated. Examples of two circuits exhibiting a zero sensitivity of ωo to the GB changes (a very desirable feature) are presented. The first example represents oscillators with a single op.-amp. whose slew-rate effect is the only oscillator non-linearity. The second example concerns oscillators with a so-called composite amplifier where non-linear elements included in the oscillator feedback network are responsible for amplitude stabilization.