(a) Find the peak-to-peak amplitude and frequency of the sawtooth output in Figure 10–32 . Assume that the forward PUT voltage, $V_{\mathrm{F} }$ , is approximately 1 V.

(b) Sketch the output waveform.

Question

(a) Find the peak-to-peak amplitude and frequency of the sawtooth output in Figure 10–32 . Assume that the forward PUT voltage, [latex] V_{\mathrm{F} }[/latex] , is approximately 1 V.

(b) Sketch the output waveform.

Accepted Answer

(a) First, find the gate voltage in order to establish the approximate voltage at which the PUT turns on.

[latex]V_{\mathrm{G}}=\frac{R_4}{R_3+R_4}(+V)=\frac{10 \mathrm{k} \Omega}{20 \mathrm{k} \Omega}(+15 \mathrm{~V})=7.5 \mathrm{~V}[/latex]

This voltage sets the approximate maximum peak value of the sawtooth output (neglecting the 0.7 V).

[latex]V_{\mathrm{P}} \cong 7.5 \mathrm{~V}[/latex]

The minimum peak value (low point) is

[latex]V_{\mathrm{F}} \cong 1 \mathrm{~V}[/latex]

So the peak-to-peak amplitude is

[latex]V_{p p}=V_{\mathrm{P}}-V_{\mathrm{F}}=7.5 \mathrm{~V}-1 \mathrm{~V}=6.5 \mathrm{~V}[/latex]

The frequency is determined as follows:

[latex]V_{\mathrm{IN}}=\frac{R_2}{R_1+R_2}(-V)=\frac{10 \mathrm{k} \Omega}{78 \mathrm{k} \Omega}(-15 \mathrm{~V})=-1.92 \mathrm{~V}[/latex]

[latex]f=\frac{\left|V_{\mathrm{IN}}\right|}{R_i C}\left(\frac{1}{V_{\mathrm{P}}-V_{\mathrm{F}}}\right)=\left(\frac{1.92 \mathrm{~V}}{(100 \mathrm{k} \Omega)(0.005 \mu \mathrm{F})}\right)\left(\frac{1}{7.5 \mathrm{~V}-1 \mathrm{~V}}\right) \cong \mathbf{5 9 1 ~ H z}[/latex]

(b) The output waveform is shown in Figure 10–33 . The period is

[latex]T=\frac{1}{f}=\frac{1}{591 \mathrm{~Hz}}=1.69 \mathrm{~ms}[/latex]

P R A C T I C E EXERCISE

If [latex]R_i[/latex] is changed to 56 kΩ in Figure 10–32 , what is the frequency?

Question 10.5: (a) Find the peak-to-peak amplitude and frequency of the saw...

Related Answered Questions

A 555 timer confi gured to run in the astable mode (oscillator) is shown in Figure 10–39 . Determine the frequency of the output and the duty cycle. ...

Verified Answer:

Determine the pulse widths and show the timing diagram (relationships of the input and output pulses) for the circuit in Figure 10–46 . ...

Verified Answer:

A 555 timer is connected as a one-shot with R ext = 10 kΩ and C ext = 0.1 mF. What is the pulse width of the output? ...

Verified Answer:

Determine the frequency of the circuit in Figure 10–30 . To what value must R 1 be changed to make the frequency 20 kHz? ...

Verified Answer:

a) Determine the frequency for the oscillator in Figure 10–21 . Assume there is negligible loading on the feedback circuit and that its Q is greater than 10. (b) Find the frequency if the oscillator is loaded to a point where the Q drops to 8. ...

Verified Answer:

a) Determine the value of Rf necessary for the circuit in Figure 10–14 to operate as an oscillator. (b) Determine the frequency of oscillation. ...

Verified Answer:

Determine the frequency for the Wien-bridge oscillator in Figure 10–12 . Also, calculate the setting for Rf assuming the internal drain-source resistance, rds’ , of the JFET is 500 Ω when oscillations are stable. ...

Verified Answer: