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Newday
New member
Username: Newday
Post Number: 1
Registered: 8-2017
| | Posted on Wednesday, August 23, 2017 - 1:56 am: | 
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I have seen an article named Audio Oscillator circuit.Can I have a discussion about it with you?
Let me introduce ICL8038 firstly.We can learn from the datasheet of ICL8038 ( \newurl www.kynix.com/uploadfiles/pdf0125/ICL8038.pdf}
), it is a monolithic waveform generator IC that can produce sine, square and triangular waveforms with very little distortion. The frequency can be programmed from 0.001Hz to 300 KHz using external timing capacitor and resistor. Frequency modulation and sweeping can be attained by using an external voltage. Other features of the ICL8038 are high linearity, high level outputs, simultaneous sine, square, triangle wave outputs, low external parts count, high temperature stability etc.
The circuit diagram given in this assay shows avariable audio frequency oscillator using ICL8038 which is useful while testing audio related projects. Here the frequency range is between 20Hz to 20KHz when POT R6 can be used for adjusting the frequency while POT R9 can be used for adjusting the distortion. POT R4 can be used for adjusting the duty cycle while POT R7 can be used for nullifying the variations in duty cycle. C2 is the external timing capacitor and R5 is a pull up resistor.
www.circuitstoday.com/audio-oscillator-circuit-2}
It also introduce that the working principle of ICL8038. For example,the first current source is on all the time and second current is switched ON and OFF using a flip-flop. The external timing capacitor is charged and discharged using two internal current sources.
I see there are are at least 3 problems in the diagram:
1). I assume the supply is +10v-0v–10v, where then is the 0v connected?
2). what forms the output of the circuit, I see the +ve sides are formed from the outputs of the IC on either pins2,3 & 9 of IC1, what forms the -ve output?
3). I appears that pin 9 of IC1 is connected via a 15K resistor to the +10v line, are there similar connections to pins 2 & 3? |
Newday
New member
Username: Newday
Post Number: 1
Registered: 8-2017
| | Posted on Wednesday, August 23, 2017 - 9:58 pm: |
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http://www.kynix.com/uploadfiles/pdf0125/ICL8038.pdf |
Tech833
Moderator
Username: Tech833
Post Number: 2386
Registered: 8-2002
| | Posted on Saturday, August 26, 2017 - 4:44 pm: |
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Good questions.
Looking at the data sheet, I did spot the sentence, "V- or ground". So it appears, -10 V could be ground.
As for question #2, without a ground or something to push/pull against, there would be no output. Assuming the -10 VDC is actually ground, then it appears that pins 9, 3, and 2 would output waveforms in reference to ground.
As for question 3, in the test circuit schematic, it shows pin ( working against the +10 VDC leg, while pins 2 and 3 each have their own resistor to ground (and again, no other reference to ground).
First thing I spotted on top of the data sheet is the chip has been discontinued and they have no replacement. There is occasionally an IC that gets produced that is a total dud and disappears very soon thereafter. This appears to be one of those poorly designed IC's.
Your radio 'Mythbuster' since 1998
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