9400-Based Voltage-to-Frequency Converter (Dual-Supply)

Figure 1.  Schematic Diagram for a Dual-Supply Voltage-to-Frequency Converter Using the 9400

Figure 1 shows the basic application circuit for using the 9400 in voltage-to-frequency (V-F) conversion.  The 9400 is a 14-pin voltage-to-frequency/frequency-to-voltage converter IC. Note that the circuit in Figure 1 needs two voltage supplies (+5V and -5V). For single supply operation, see this circuit.

The output frequency Fo of this circuit is given by:  Fo = (Vin / (Vref x Rin x Cref)).  The values chosen for the circuit in Figure 1 can give an output frequency ranging from 10 Hz to 10 kHz.