People came up with various ways of designing these. The way I remember from Walsall College of Technology many years ago goes like this- Start by choosing your Supply voltage,Collector load resistor value and a suitable Transistor. The Emitter resistor is then one tenth of the value of the Collector load one. We need to have an idea of the transistors hfe ideally at the quiescent collector current we have chosen but we could use one of those Digital Multimeters with the hfe measuring function for a rough idea. We know that we want half the supply voltage dropped across the Collector load and we know the Collector load's value so we can calculate the quiescent collector current using ohm's law. We can calculate the quiescent base current by dividing collector current by hfe. Now we can calculate the voltage across the Emitter resistor using ohm's law since we know the resistance of this and the quiescent emitter current flowing through it which is of course the collector and base quiescent currents added together. If we now take this emitter voltage figure and add 0.6V (assuming a silicon transistor) to it we have the base voltage. Now we can use ohm's law to calculate the lower bias divider resistor value as we know the voltage across it and that we want ten times the base current flowing through it (the ten times base current flow is to keep the operating point stable). We can also use ohm's law to calculate the upper bias divider resistor value as the voltage across it is simply the supply voltage minus the base voltage and the current flowing through it is ten times the base current plus the base current. Time to power up and check the collector voltage and tweak the value of the upper bias divider resistor if the voltage here is too far away from half of that of the supply. The three capacitors-two for coupling and one for emitter-bypass could also be calculated to specify how far down we want the low freguency response to go but I suggest just picking out favourite values here to simplify things. I hope this helps.
Very good Clem!I like using the Collector-Base bias method to get to Class A myself.The four resistor way of doing things (sometimes called H Bias) is considered superior though with the best gain etc.I wonder if we might see you make up one of these in the future?It would be educational.
@@CoolDudeClem it means all the preamplifier designs have this loop holes there is no solution for it to .it is very disappointing that i am hearing from an expert
Sorry but he's wrong in this instance. Provided the noise is actually being picked up by your transistor pre-amp circuit and not the actual hardware inside the laptop, there's plenty you can do to smooth out voltage from a noisy SMPS. Connect your circuit via any of the following- Another voltage regulator (eg MP1584 or LM2596 module) DC-DC isolator Diode & smoothing capacitors LC Filter module
I know I am late to the party, but if your mic is getting him, it could be any of a few things. If it's ground loop, you can place resistor and ceramic cap across input and ground to help quiet it out. If it's the 50/60Hz him from a PSU, try using a linear regulator, there are small ones the size of a transistor that can do 3.3v 100ma, perfect for the mic capsule. I try and use above tricks before transformers, they can get expensive and take space.
That 100 ohm resistor and the 100uf capacitor are there to smooth out any remaining ripple (power supply hum) so the microphone gets perfectly clean DC. You don't want any ripple noise getting amplified, so those filter the ripple out.
You could do a video in which you're talking about the history of your youtube channel. Why you created it, and how your channel has evolved in the past 11 years. You're just only 110 subs away from reaching 10K subs. It would be fun to see such video from you.
Just what I needed as I have salvaged several of these mics and have a few uses for them. I get what you are doing with the voltage dividers but should the 2.2m resistor stay the same if I'm running off 5V. Thanks. Great voices too 😀
I forgot I'd left that part where I was just goofing off in! But yeah it should work just fine on 5 volts without changing the 2.2M resistor, you might want to change the resistor for the microphone though, maybe something like 10k instead of 18k for 5 volts.
@@CoolDudeClem THANKS. i was searching on this topic and have seen every video on you tube of making and amplifier using single transistor your are explaining better then any you tuber. i have a QUESTION that can i hear its sound by connecting directly its leads to speaker ? i have seen your video now i will make it
THANKS. i was searching on this topic and have seen every video on you tube of making and amplifier using single transistor your are explaining better then any you tuber. i have a QUESTION that can i hear its sound by connecting directly its leads to
I'd say it's just about right, at least for my intended use where you hold it between 1 and 2 feet away and don't have to practically swallow the mic to be heard.
It should still work from a 5 volt supply, just remember that most of those have a lot of ripple in their output, so put a 100 ohm resistor in series with the supply, along with a capactir of 1000uf across he pwer inputs for the preamp and that should filter the noise out.
Very good circuit. Most people never show the output through a speaker and I appreciate that
People came up with various ways of designing these.
The way I remember from Walsall College of Technology many years ago goes like this-
Start by choosing your Supply voltage,Collector load resistor value and a suitable Transistor.
The Emitter resistor is then one tenth of the value of the Collector load one.
We need to have an idea of the transistors hfe ideally at the quiescent collector current we have chosen but we could use one of those Digital Multimeters with the hfe measuring function for a rough idea.
We know that we want half the supply voltage dropped across the Collector load and we know the Collector load's value so we can calculate the quiescent collector current using ohm's law.
We can calculate the quiescent base current by dividing collector current by hfe.
Now we can calculate the voltage across the Emitter resistor using ohm's law since we know the resistance of this and the quiescent emitter current flowing through it which is of course the collector and base quiescent currents added together.
If we now take this emitter voltage figure and add 0.6V (assuming a silicon transistor) to it we have the base voltage.
Now we can use ohm's law to calculate the lower bias divider resistor value as we know the voltage across it and that we want ten times the base current flowing through it (the ten times base current flow is to keep the operating point stable).
We can also use ohm's law to calculate the upper bias divider resistor value as the voltage across it is simply the supply voltage minus the base voltage and the current flowing through it is ten times the base current plus the base current.
Time to power up and check the collector voltage and tweak the value of the upper bias divider resistor if the voltage here is too far away from half of that of the supply.
The three capacitors-two for coupling and one for emitter-bypass could also be calculated to specify how far down we want the low freguency response to go but I suggest just picking out favourite values here to simplify things.
I hope this helps.
Thanks for sharing more about one transistor amplifier
FOR SOME REASON I GOT A LOT OF NOISE WHEN I CONNECT SUCH CIRCUIT TO AND ONE MOSFET AUDIO AMP ........ HELP PLEASE .......
Great job squeezing in all that on there and great design, works well, it’s great when something works hey?
Very good Clem!I like using the Collector-Base bias method to get to Class A myself.The four resistor way of doing things (sometimes called H Bias) is considered superior though with the best gain etc.I wonder if we might see you make up one of these in the future?It would be educational.
In my experience I haven't had the best luck with those, but it's definitely something I might experiment with.
Is it save to replace the condenser mic with a dynamic mic, or would that require any changes?
yes that's entirely possible, and you can omit the resistor that "powers" the mic, as a dynamic mic doesn't need power.
What is solution for hum coming into the preamp through using mic when laptop charger is connected to the laptop
Not much can be done about that, most chargers have a lot of electrical noise.
@@CoolDudeClem it means all the preamplifier designs have this loop holes there is no solution for it to .it is very disappointing that i am hearing from an expert
Sorry but he's wrong in this instance. Provided the noise is actually being picked up by your transistor pre-amp circuit and not the actual hardware inside the laptop, there's plenty you can do to smooth out voltage from a noisy SMPS. Connect your circuit via any of the following-
Another voltage regulator (eg MP1584 or LM2596 module)
DC-DC isolator
Diode & smoothing capacitors
LC Filter module
I know I am late to the party, but if your mic is getting him, it could be any of a few things. If it's ground loop, you can place resistor and ceramic cap across input and ground to help quiet it out.
If it's the 50/60Hz him from a PSU, try using a linear regulator, there are small ones the size of a transistor that can do 3.3v 100ma, perfect for the mic capsule.
I try and use above tricks before transformers, they can get expensive and take space.
Hello! Would I be able to use a 2N222A.. would it be able to handle the super-high frequencies?
Yes 2n2222 will also have more gain
This was awesome and very cool to see. The only thing I didn't understand is what the 100 ohm resistor is for right by the 12v source?
That 100 ohm resistor and the 100uf capacitor are there to smooth out any remaining ripple (power supply hum) so the microphone gets perfectly clean DC. You don't want any ripple noise getting amplified, so those filter the ripple out.
Are you going to record something special for us when you hit the 10000 subscriber milestone?
I'll probably do something, I didn't even know I was close to 10000!
You could do a video in which you're talking about the history of your youtube channel. Why you created it, and how your channel has evolved in the past 11 years. You're just only 110 subs away from reaching 10K subs. It would be fun to see such video from you.
Just what I needed as I have salvaged several of these mics and have a few uses for them. I get what you are doing with the voltage dividers but should the 2.2m resistor stay the same if I'm running off 5V. Thanks. Great voices too 😀
I forgot I'd left that part where I was just goofing off in! But yeah it should work just fine on 5 volts without changing the 2.2M resistor, you might want to change the resistor for the microphone though, maybe something like 10k instead of 18k for 5 volts.
@@CoolDudeClem Thanks 😀
@@CoolDudeClem THANKS. i was searching on this topic and have seen every video on you tube of making and amplifier using single transistor
your are explaining better then any you tuber.
i have a QUESTION that can i hear its sound by connecting directly its leads to speaker ? i have seen your video now i will make it
My transistor is making way to much noise,
THANKS. i was searching on this topic and have seen every video on you tube of making and amplifier using single transistor
your are explaining better then any you tuber.
i have a QUESTION that can i hear its sound by connecting directly its leads to
Mic sounds good. Gain a bit too high?
I'd say it's just about right, at least for my intended use where you hold it between 1 and 2 feet away and don't have to practically swallow the mic to be heard.
@@CoolDudeClem i had to login to like reply - `swallow the mic`
Please, do this with power supply from USB 5V, and the connection to USB port !
It should still work from a 5 volt supply, just remember that most of those have a lot of ripple in their output, so put a 100 ohm resistor in series with the supply, along with a capactir of 1000uf across he pwer inputs for the preamp and that should filter the noise out.
@@CoolDudeClem Thank you!
Thanks for sharing!!
U r awesome 👏✊👍
i am waiting for your replay
Blah blah blah boring
Then don't watch, I'm not holding you at gunpoint forcing you to watch.