The experiment use inverter gate as oscillator circuit. We will try to take an inverter gate to test fun circuit. The inverter that use is CMOS also be use the number : MC14069B. Or if not have used the old NAND gate : MC14011B. Then, take input joint together into the same inverter form.
Connect circuit as Figure 1 (below) in picture on breadboard. In picture will show pin number of IC for connecting circuit at input and output of gate. Just to joint pin by many wires onto the breadboard as correct position only.
In Figure will see that connecting the inverter I1-I4 in continuously series, output of I3 will feed back to input of I1. Thus, the signal will run from I1 to I3 and backward to I1 in cycle form.
We used an oscilloscope to measure the signal to see waveform at output of I4, will see that the square wave form signal have high frequency about 3.3 MHz.
But if not have the oscilloscope, you can test this circuit with apply it near the antenna of television, we will see that on screen will have more many dot like the rain, indicated the circuit is working with high frequency.
This circuit is oscillated easily by has the principle that the input and output of inverter will always opposite, and the signal that entered to input of each gate before will appear at that output, will be must has a little delay time. Try to see circuit in Figure 1 new again.
Suppose that, at input of I1 is “0” output at pin 11 will be “1”. This signal “1” will be entered to input of I2 and provide the output “0”. That is signal “0” fed back as “1” with I3, then is fed back is the input of I1 new.
Therefore at input of I1 will change from “0” into “1” automatically, and this signal “1” when flow through to I4 and new cycle will be “0”.
Thus, the signal will be “0” and “1” alternately at all the time.
Figure 1 The experiment the inverter digital gate as the square wave oscillator circuit.
Connecting the inverter circuit as the oscillators, we have top how is must use the gate as odd number such as 1, 3, 5…. etc.
If even number will not cause oscillated. Also,the frequency of waveform that oscillated and depends on the delay time of each gate, and also amount of the gate. The CMOS will have the delay time approximately 0.1 uS.
Therefore, if use the 3 gate connected as the delay time of 0.3 micro second. So, the output frequency of 3.3 MHz.
The gate is TTL type will has delay time about 20 nanosecond. Which faster than CMOS of 5 times.
If take this demonstrations will can get frequency waveform approximately 15 MHz.
The demonstrations also has very useful in measuring the delay time of gate.
Which we can calculate backward from the oscillated frequency.
Suppose that, in cycle of gate,if has some thing makes long delay time up, will makes the frequencies is certainly lower. By we connected a little capacitor across the inverter as Figure above.
When we insert the capacitor connects between the input and output of I2 will cause the delay time at the I2 is longer up. After that, try to measure the waveform will see that have lower frequencies.
If try to change the capacitance will find that, If capacitor is larger up will delay up had result to reduce frequency down, as table that show in Figure 1 that.
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