Need an amplifier.

[Marks256]

I need to amplify a 5 volt digital signal to a 9-12volt digital signal. How would i do this? I have an 1kohm center-tapped to 8ohm audio output transformer. I also have 2 2n3906 transistors, and 6 2n3904 transistors.
I tried Google, but i wasn't quite sure what to search for. I searched for "Antenna amplifier", "Digital Amplifier", "Antenna booster", and a few others.

In case you are wondering what i am doing, i will try to explain. I am building a RF Scrambler. It works very well. But i have to be standing right next to the radio to use it. This isn't acceptable. I need to be able to transmit the scrambling signal about 50ft+.

Please help. Thanks.

 

[Papabravo]

You can use one of your 2N3904 NPN transistors to make a class A linear amplifier. The output of this amplifier will invert the input, but for your purposes that should not matter.

 

[Marks256]

ok. I just spent about 15min looking for a circuit, but i could not find any that involved an NPN transistor. Could you point me in the right direction?

 

[Analog]

I need to amplify a 5 volt digital signal to a 9-12volt digital signal. How would i do this? I have an 1kohm center-tapped to 8ohm audio output transformer. I also have 2 2n3906 transistors, and 6 2n3904 transistors.
I tried Google, but i wasn't quite sure what to search for. I searched for "Antenna amplifier", "Digital Amplifier", "Antenna booster", and a few others.

In case you are wondering what i am doing, i will try to explain. I am building a RF Scrambler. It works very well. But i have to be standing right next to the radio to use it. This isn't acceptable. I need to be able to transmit the scrambling signal about 50ft+.

Please help. Thanks.

I don't understand quite what you want. It sounds like you want an RF amplifier? For that, you need to be specific for the frequency of transmission. These are generally difficult to build due to RF design rules and parasitics. Unless your talking AM radio...

If I'm correct about the need for an RF amp, then your 3904s may be useless at the RF frequencies interested (depends on how high of a frequency - Cellphone???), you're going to need appropriate RF transistors for this design. So perhaps you need to google RF amplifier and then be sure to get the right frequency range to get appropriate hits. Otherwise others on this forum could help id a good circuit..

 

[Papabravo]

There is RF and there is nervous DC. I believe a 2N3904 will be able to manage a gain of 2 at 1-2 MHz. since it has a GBW of 300MHz.

Common Emitter Amplifier

 

[Marks256]

Yes, i need an RF ampli. The thing is, i don't know what the frequency of it is. I mod-ed the circuit to go higher than the original frequency. Basically what i have done, is made a 555 digital clocking circuit, and then ran the I/O into an inverter. I need to amplify this frequency. Any more ideas?

 

[zachtheterrible]

Hi Marks, look in the projects section of this forum for audioguru's FM transmitter, it has a 2n3904 amplifier that amplifies signals at 100MHZ (its the transistor furthest to the right on the schematic). What frequency are you trying to jam? and could I see your circuit? sounds interesting.

 

[Overclocked]

Make the 555 Timer go faster. If you want to transmit, you'll need 2 signals. The signal you want to transmit, and the carrier.

 

[Marks256]

Make the 555 Timer go faster. If you want to transmit, you'll need 2 signals. The signal you want to transmit, and the carrier.

What is the carrier? Is it the actual frequency that you are running at? I am not trying to transmit useful things, just fuzz.

Hi Marks, look in the projects section of this forum for audioguru's FM transmitter, it has a 2n3904 amplifier that amplifies signals at 100MHZ (its the transistor furthest to the right on the schematic).

I will check that out when i get a chance.

What frequency are you trying to jam?

All AM and FM in a few hundred feet radius. I have a POT that allows me to "fine tune" to a frequency.

and could I see your circuit? sounds interesting.

Sure. I will draw up a schematic before i go to bed tonight, then i will post it either tonight, or in the morning. It probably isn't very complex to you guys, but hey, i think it is cool(only because this is my first circuit that i made, that does something ).

 

[Overclocked]

Doesnt matter if your transmitting something useful or not, You still need a carrier. A carrier is what Carries the signal. For example, a 100Mhz signal, when modulated with data using a mixer (transistor, opamp..diode..etc), that data will be transmitted along with the 100Mhz signal. The radio decodes the carrier and then you have the information you sent.

Think of carrier like a Carrier Pigion, or a Car with people in it. When the car gets to where it has to go, The people get out.

 

[Marks256]

Oh, ok. I get it now. Thanks.

Also, i looked at that circuit, but it didn't have any 3904's in it, just 2222's??

 

[audioguru]

The fundamental frequency of a 555 timer goes up to only about 1MHz which is in the middle of the AM broadcast band.. Its harmonics go much higher but are reduced in amplitude. I doubt that the harmonics would interfere with an FM radio at 100MHz.

My FM transmitter uses 2N3904 transistors that are about the same as 2N2222, BC547 and many other general purpose transistors.

 

[audioguru]

Oh yeah, I forgot.
If you want a 12V signal from a 555 timer then power it with a 13.5V battery, its max is 15V to 18V (depending on the manufacturer). The max voltage for a Cmos 555 is 12V to 15V.

 

[Marks256]

No, i was able to completely knock out 96.5 from about a foot away. I have given up on the circuit. I had no use for it anyways. Here is the link i got the oscillator from, i just added an antenna, and a hex inverter.
https://www.electronic-circuits-diagrams.com/oscillatorsimages/oscillatorsckt1.shtml

The reason for the hex inverter is to let the first clock cycle be 0->1, instead of 1->0. I will just use it as a clock until i am able to figure out how to use a crystal. Thanks.

 

[audioguru]

i just added an antenna, and a hex inverter.

It is the fast edges of the output from the hex inverter that creates harmonics up to the FM broadcast band. The output of a 555 timer is too slow by itself.

 

[Marks256]

It is the fast edges of the output from the hex inverter that creates harmonics up to the FM broadcast band. The output of a 555 timer is too slow by itself.

So the hex inverter is the only reason it worked?

 

[audioguru]

So the hex inverter is the only reason it worked?

Yeah. A Cmos hex inverter is used as an FM transmitter where its 9th harmonic of a 10.7MHz oscillator is at 96.3MHz:

 

[Marks256]

Oh, i see. If you hook up more than one inverter in a parallel, then you will get more output? Also, what is that symbol for the "crystal", is that a 2 pin crystal, with the can grounded, or is it a crystal oscillator(the 4 pin thingy)?

 

[audioguru]

If you hook up more than one inverter in a parallel, then you will get more output?

The output current of a Cmos inverter is low. Connecting 3 in parallel provides 3 times the output current.

Also, what is that symbol for the "crystal", is that a 2 pin crystal, with the can grounded, or is it a crystal oscillator(the 4 pin thingy)?

It has 3 pins (input, output and ground) and it is clearly labelled as a 10.7MHz ceramic filter that is something like a crystal. It is used in FM radios.

 

[Marks256]

It has 3 pins (input, output and ground) and it is clearly labelled as a 10.7MHz ceramic filter that is something like a crystal. It is used in FM radios.

Well, i am sorry i didn't know what that was. I guess is should have googled it instead of asking. Sorry.