I am looking for a possibility to design a frequency-variable Wien Oscillator on an ASIC. Since I cannot use potentiometers, I am searching for an alternative.
Initially, I was thinking about using a MOSFET in triode region as voltage controlled resistor. However, since I am dealing with transient signals here (sine wave), the respective resistance is fluctuating for these components and thus corrupting the output signal's frequency.
Maybe someone could help me out? I am working in X-FAB's 180nm technology.
Dear Frederik, since the frequency of oscillation only depends on R and C, you can also use a varactor to change the capacitance. You may also consider high linearity switches or capacitance banks if you will have a discrete control mechanism.
Hello dear Frederik Lesniewski
I think the problems will not arise only due to the method(s) for tuning the resistance (or capacitance) values electronically.
In Wien oscillator, if only one resistor's (or one capacitor's) value is adjusted to change the frequency of oscillation, the condition of oscillation will also be altered. The condition of oscillation dictates the amplifier's gain value to be chosen according to the ratio of resistor values and ratio of capacitor values.
On the other hand, if, you can tune two resistors (or capacitors) together in harmony, then you can manage to keep the condition of oscillation almost unchanged. Thus, you can increase the chance to change the frequency of oscillation without harming the functionality of the oscillator.
Of course, maintaining a "parallel" tuning of devices electronically for THIS oscillator will be even more challenging due to the asymmetrical connections of the devices.
Last but not least: The amplifier will also need a gain control mechanism for keeping the output signal amplitude at the desired value. Actually, this control can also relax the concerns related with condition of oscillation. Even when condition of oscillation is altered a little bit, this control can prevent the "fading away" or "saturation" of the output signal.
Best regards...
You can try to use tunable floating and grounded resistors with operational transconductance amplifiers, as proposed in the attached file. The frequency tuning is linear and made through the bias current IB (or Ibias to the grounded resistor).
Implementing a frequency-tunable Wien Bridge oscillator on an integrated circuit (IC) involves designing the circuitry using suitable components and techniques. Here is a general approach to realizing a frequency-tunable Wien Bridge oscillator on an IC:
- Badges
- Science topic
- Similar topics
- Filing