FM SIGNAL GENERATOR OR WOBBULATOR

Description: A sine-wave input can be applied to an RCA CA3046 transistor array configured as a voltage-controlled oscillator (VCO), which functions effectively as a low-distortion frequency modulation (FM) signal generator. When a sawtooth input is utilized, the same configuration operates as a wobbulator. Increasing the size of the timing capacitor decreases the operating frequency, allowing the circuit to be used down to audio frequencies, making it suitable as a voltage-controlled oscillator in electronic organs.

The RCA CA3046 is a versatile integrated circuit that contains multiple transistors and can be employed in various applications, including as a voltage-controlled oscillator (VCO) and a wobbulator. In the VCO configuration, the transistor array generates low-distortion FM signals when driven by a sine-wave input. This is particularly useful in communication systems where high fidelity is required.

In the wobbulator configuration, the circuit can produce frequency modulation effects by using a sawtooth input. This is beneficial in audio applications where modulation of sound frequencies is desired, such as in synthesizers or effects processors. The sawtooth waveform allows for a smooth transition between frequencies, creating a rich modulation effect.

The timing capacitor in the circuit plays a crucial role in determining the frequency of oscillation. By selecting a larger timing capacitor, the oscillation frequency can be reduced significantly, enabling the circuit to operate effectively at audio frequencies. This feature is particularly advantageous for electronic organs, where the ability to control pitch dynamically is essential for sound synthesis.

The RCA CA3046's design allows for easy integration into various electronic systems, and its flexibility makes it a popular choice among engineers designing audio and communication circuits. Properly implementing this circuit requires careful consideration of component values, particularly the timing capacitor and resistors, to achieve the desired frequency response and stability.With sine-wave input, RCA CA3046 transistor array connected as VCO can be used as low-distortion FM signal generator. With sawtooth input, same arrangement serves as wobbulator. Increasing size of timing capacitor reduces op-erating frequency, permitting use down to audio frequencies as voltage-controlled oscillator in electronic organ.

-J. L. Lins ley Hood, Linear Voltage Controlled Oscillator, Wireless World, Nov, 1973, p 567-569.