**External Connections**

**20 kHz Quadrature Oscillator**
The FDI-4423 does not require and external components to obtain a 20 kHz quadrature oscillation. The connection diagram is shown in Figure 1.

Figure 1

**Resistor Programmable Quadrature Oscillator**

For resistor programmable frequencies in the 2 kHz to 20 kHz frequency range the connection diagram is provided in Figure 2. Note that only two resisters of equal value are required. Resistor values are found using Equation 1.

(1)

Where R is in KΩ and f is in kHz.

Figure 2

**Quadrature Oscillator Programmable to 0.02 Hz**

For oscillation frequencies below 2 kHz the addition of two resistors and two capacitors of equal value is required. The connections of Figure 3 should be used. The frequency of oscillation can be found using Equation 2.

(2)

Where f is in Hz, C is in µFd, and R is in KΩ.

Alternately you can select a capacitance using Figure 4 and calculate the resistance required using Equation 3.

Where R is in KΩ, f is in Hz, and C is in µFd.

**Recommended Capacitor Values**

For best results use capacitor values shown in Figure 4 for each frequency range. It is important that the two capacitors be as close to the same value as possible.

**Recommended Capacitor Types **

The FDI-4423 Quadrature Oscillator will only work with non-polarized capacitors with Dissipation Factors of less than 0.01 (or 1%). Best results will be obtained using ceramic capacitors.

**Oscillation Amplitude**

Depending on the frequency it can take a long time to build up to the full output amplitude. In general the lower the frequency the longer it takes the oscillation to start.

There are two methods that can be used to shorten the start up time:

Method one involves adding a large value resistor between pins 3 and 14 of the FDI-4423. The lower this resistor the quicker the oscillation will start but the worse the distortion of the two outputs. A typical value to try would be 100 KΩ.

Method two is similar to method one but the resistor is inserted only during start up of the oscillation. For instance if a 1 KΩ resistor in series with a push button is installed between pins 3 and 14 and the button pushed during start up the oscillator will start quickly and then will revert to low distortion after the button is released.

**Low Frequency Operation**

At low frequencies there may be problems getting the Quadrature Oscillator to start oscillating. Placing a resistor between pins 3 and 14 can cure this problem. For instance a 34KΩ resistor can be used in the 0.2 Hz to 2 Hz range.

**Uncommitted Op Amp**

Pins 4, 5, and 6 of the FDI-4423 are connected to an Op amp that is available to be used. It can be used as a buffer or gain stage. If this Op Amp is not used then pins 4 and 5 of the FDI-4423 should be connected to power supply ground.