# How to control the frequency of an oscillator consisting of a single transistor

#### Mars Park

Joined Feb 20, 2022
37

I made the circuit as above. When I checked the voltage at the collector, I got the following signal.

The frequency is too high. I want to lower frequency. Targets range from about 100 kHz to 200 kHz. Please teach me the way.

#### Papabravo

Joined Feb 24, 2006
20,984
I'm not sure you have an oscillator with a frequency you can predict or control. How were you planning on controlling it?
I kind of remember things like that from 60 years ago, but I never had occasion to use one because many better alternatives were available.

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#### Mars Park

Joined Feb 20, 2022
37
I'm not sure you have an oscillator with a frequency you can predict or control. How were you planning on controlling it?
I thought the frequency would change if I changed the resistance and cap values. Am I wrong?

#### Papabravo

Joined Feb 24, 2006
20,984
Changing the resistors will change the DC bias on the transistor. Usually, an oscillator wants a stable bias so I'm not sure that is a useful way to go. What are you trying to accomplish with this monstrosity?

#### Mars Park

Joined Feb 20, 2022
37
Changing the resistors will change the DC bias on the transistor. Usually, an oscillator wants a stable bias so I'm not sure that is a useful way to go. What are you trying to accomplish with this monstrosity?
I would like to output a voltage of 1kV to 2kV. A multiplier is connected to the secondary side of the transformer.
I made the transformer myself. The transformer worked well at 100 kHz. The 23 MHz frequency did not transform well.

#### AlbertHall

Joined Jun 4, 2014
12,324
The phasing of the base and collector windings looks wrong. Try reversing the connections to one of the windings if they are actually wired that way.

#### Ramussons

Joined May 3, 2013
1,390
It is a Hartley Oscillator made a little confusing.

The frequency can be varied by changing the Tank capacitor, C1

#### LowQCab

Joined Nov 6, 2012
3,925
A Square-Wave-Oscillator would be more efficient when driving a Voltage-Multiplier,
and eliminating the Voltage-Multiplier,
and increasing the Transformer-Secondary-Turns,
would be even more efficient.

How much Current do You need at ~2K-Volts ?
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#### Mars Park

Joined Feb 20, 2022
37
A Square-Wave-Oscillator would be more efficient when driving a Voltage-Multiplier,
and eliminating the Voltage-Multiplier,
and increasing the Transformer-Secondary-Turns,
would be even more efficient.

How much Current do You need at ~2K-Volts ?
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I need about 250uA, that is, 500mW.

#### Mars Park

Joined Feb 20, 2022
37
The phasing of the base and collector windings looks wrong. Try reversing the connections to one of the windings if they are actually wired that way.
Yes, thank you. I'll give it a try.

#### atferrari

Joined Jan 6, 2004
4,746
I am not an expert at all, but after actively learning the basics of the most common topologies, for 1,2 MHz, found the Clapp oscillator not difficult to deal with.

#### LowQCab

Joined Nov 6, 2012
3,925
Use an SG2524 IC Regulator/Controller ( DIP-16 ),
DigiKey p/n 296-9685-5-ND,
<~$2.oo, >~800 in stock, easy to work with, Fully-Symmetrical-Push-Pull-Output, Adjustable-Frequency, Current-Limited, Voltage-Regulated-Output, very stable with varying Loads, electrically very quiet for an SMPS Power-Supply ---> easier to filter Output. ( may require one very small additional Transformer-Winding for monitoring Output-Voltage, this is easier than trying to "pad-down" the extremely high Output-Voltage for Regulation-Feedback ). https://www.digikey.com/en/products/detail/microchip-technology/SG2524N/13472606?s=N4IgjCBcpgbFoDGUBmBDANgZwKYBoQB7KAbXAAYB2ADkoE4QBdAgBwBcoQBlNgJwEsAdgHMQAXwJg61BtBDJI6bPiKkQ5Jqw6RufIaIkgAtPDkK+AVxXFIZAMxNDRgEwJ5US9bUNGYw69tuAHFnAFZnABZHIA . . . #### Attachments • 2.1 MB Views: 4 Last edited: #### ci139 Joined Jul 11, 2016 1,898 #### AlbertHall Joined Jun 4, 2014 12,324 Thread Starter #### Mars Park Joined Feb 20, 2022 37 The phasing of the base and collector windings looks wrong. Try reversing the connections to one of the windings if they are actually wired that way. Thank you. you were right. When I changed the direction of the feedback winding, the frequency dropped. I succeeded in making 1kV output. Thank you. Thread Starter #### Mars Park Joined Feb 20, 2022 37 Use an SG2524 IC Regulator/Controller ( DIP-16 ), DigiKey p/n 296-9685-5-ND, <~$2.oo, >~800 in stock,
easy to work with,
Fully-Symmetrical-Push-Pull-Output,
Current-Limited,
Voltage-Regulated-Output,
electrically very quiet for an SMPS Power-Supply ---> easier to filter Output.
( may require one very small additional Transformer-Winding for monitoring Output-Voltage,
this is easier than trying to "pad-down" the extremely high Output-Voltage for Regulation-Feedback ).

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First of all, I purchased the parts you recommended. It looks like I can make high voltage more stable. However, it will take time for me to receive the parts and understand the datasheet. Anyway, thank you for the advice.

#### ci139

Joined Jul 11, 2016
1,898
. . . what you miss here is that the article claims the oscillator being a resonant type . . . however i tend to believe - it has little effect (a narrow outp regulation range/capability) at this particular osc. . . . however - if the cause for such effect is being studied and anderstood - one can design a better variant with a wider reg.-n range
note. : it's easy to label people idiots - not seeing what they actually have said of value

#### Delta Prime

Joined Nov 15, 2019
1,311
note. : it's easy to label people idiots - not seeing what they actually have said of value
When a person or situation is called dodgy, it's a clue that they should be dodged if at all possible. Over unity is a no no to discuss.
I believe it was only an abundance of caution.

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#### Mars Park

Joined Feb 20, 2022
37
Use an SG2524 IC Regulator/Controller ( DIP-16 ),
DigiKey p/n 296-9685-5-ND,
<~\$2.oo, >~800 in stock,
easy to work with,
Fully-Symmetrical-Push-Pull-Output,
Current-Limited,
Voltage-Regulated-Output,
electrically very quiet for an SMPS Power-Supply ---> easier to filter Output.
( may require one very small additional Transformer-Winding for monitoring Output-Voltage,
this is easier than trying to "pad-down" the extremely high Output-Voltage for Regulation-Feedback ).

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I'm not used to looking at the datasheet, so I just don't understand. Can you tell me how to drive this chip? Or just 'Refer to a few pages of the datasheet'.

#### LowQCab

Joined Nov 6, 2012
3,925
Reading a Data-Sheet is just like learning any other subject,
You have to start by getting simple definitions of every single word that You don't completely understand,
after a few years of doing this, You will start to see that newer types, or more complex types,
of Circuits and Circuit-working-principles start to make much more sense.
Just keep on pushing and asking questions and you'll start becoming more competent.
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This Schematic has errors on the Output Filter, (missing Resistor), and on the attachment point of
the Output-Voltage-Feedback-Wire, which should be attached after the first stage of the Filter, not the second stage.
Also, the values of the Oscillator-components have not been added to the Schematic.
Otherwise it works well as shown.

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