audioguru2
- Apr 6, 2004
- 12,026
- Joined
- Apr 6, 2004
- Messages
- 12,026
Hi,
If you just want to make a negative 12V supply to be used with the 12V positive supply, a bridged amp (two amps, driven out-of-phase, and a speaker connected between them) effectively doubles the voltage for up to 4 times the output power than a 12V amp.
Most car radios today use that technique, and you can buy it in a single cheap and simple IC.
I bet your car radio (if it is fairly new) already has amps like that. Your problem is probably that the cheap speakers are 20 ohms and therefore draw only 2.8W.
Most car radios can deliver between 14W to 20W (depends on the supply voltage, 12V to 14.4V) RMS per channel to a good 4 ohm speaker.
If you just want to make a negative 12V supply to be used with the 12V positive supply, a bridged amp (two amps, driven out-of-phase, and a speaker connected between them) effectively doubles the voltage for up to 4 times the output power than a 12V amp.
Most car radios today use that technique, and you can buy it in a single cheap and simple IC.
I bet your car radio (if it is fairly new) already has amps like that. Your problem is probably that the cheap speakers are 20 ohms and therefore draw only 2.8W.
Most car radios can deliver between 14W to 20W (depends on the supply voltage, 12V to 14.4V) RMS per channel to a good 4 ohm speaker.
audioguru2
- Apr 6, 2004
- 12,026
- Joined
- Apr 6, 2004
- Messages
- 12,026
Hi again,
You show a simple voltage divider that gives a "virtual ground" like all single-supply opamp circuits use. I thought you were building a "power" amp for your radio, that would need a conplicated high-power supply like this one from the same site:
http://sound.westhost.com/project89.htm
If you use only 12V total for your amp's supply, and if your design allows its output transistors to saturate well, it will provide only about 1.7W RMS at clipping to an 8 ohm speaker, which isn't much more than a Walkman.
You show a simple voltage divider that gives a "virtual ground" like all single-supply opamp circuits use. I thought you were building a "power" amp for your radio, that would need a conplicated high-power supply like this one from the same site:
http://sound.westhost.com/project89.htm
If you use only 12V total for your amp's supply, and if your design allows its output transistors to saturate well, it will provide only about 1.7W RMS at clipping to an 8 ohm speaker, which isn't much more than a Walkman.
Kevin Weddle
- Feb 23, 2004
- 1,620
- Joined
- Feb 23, 2004
- Messages
- 1,620
You need a charge pump. This will give you plenty of current if done right too. You can design one with transistors. I'll post the circuit. I am sorry but the output is only -5V and not -10V.
View attachment 36381
View attachment 36381
Last edited by a moderator:
audioguru2
- Apr 6, 2004
- 12,026
- Joined
- Apr 6, 2004
- Messages
- 12,026
Hi Guys,
IC manufacturers have stereo (dual amps) headphones amp ICs with a built-in charge pump that developes a negative voltage for higher output, the elimination of a large output capacitor and the ability to operate from just 1 or 2 battery cells.
Philips and others have a stereo car radio amp IC with a built-in voltage doubler charge pump to multiply its bridged amps power by another factor of 4 times (the bridged amps also multiply the power by 4 times). It even switches automatically from normal voltage to boosted voltage to reduce heating. Inside the IC, the bridged amps operate out-of-phase to reduce draining of the boosted voltage.
You wanna make an IC with transistors? The ICs have at least 50 transistors and cost as little as just a few individual transistors.
IC manufacturers have stereo (dual amps) headphones amp ICs with a built-in charge pump that developes a negative voltage for higher output, the elimination of a large output capacitor and the ability to operate from just 1 or 2 battery cells.
Philips and others have a stereo car radio amp IC with a built-in voltage doubler charge pump to multiply its bridged amps power by another factor of 4 times (the bridged amps also multiply the power by 4 times). It even switches automatically from normal voltage to boosted voltage to reduce heating. Inside the IC, the bridged amps operate out-of-phase to reduce draining of the boosted voltage.
You wanna make an IC with transistors? The ICs have at least 50 transistors and cost as little as just a few individual transistors.
Similar threads
