Using Tip 122 power amp

[sreerajps]

I have a signal generator 10Hz- 1Mhz. 5v-15v adjustable. I want to drive a simple coil wonted on a core. Its changes the N-S poles according the signal frequency. But i want it with high current using TIP122. I have another source of 48V 2A DC. Do i need any additional series resistance with the sig gen to base of tip ? please help me? Can i drive this tip122 with signal generator ? :?:

 

[IanP]

Do i need any additional series resistance with the sig gen to base of tip?

Yes, you do ..
Try 1k ..

:wink:
IanP

 

[sreerajps]

Is this is the way to connect ? :arrow: diagram is attached.
The winding still works if it directly connected to the sig gen. But i need a forceful pull push with the field. So i should apply some more current in to the winding.

 

[mister_rf]

Don’t forget about a standard protection which puts a diode in antiparallel with the inductive load.

 

[alexan_e]

The TIP1xx series Darlingtons have internal reverse-EMF protection diodes, as they're made for driving inductive loads, it shouldn't be necessary to add more external diodes.

Alex

 

[sreerajps]

Don’t forget about a standard protection which puts a diode in antiparallel with the inductive load.

the current through the inductor might not stop immediately at switch-off if the diode in anti parallel is absent. It that u meant ? Or else what is the purpose of it? So the above diagram i almost right.. Is int it? But its not working at all.

 

[alexan_e]

The transistor in your schematic can only sink current so it can only turn on off the current of the coil, if I understand correctly you want to be able to apply to the coil pulses that change polarity so you will probably need an H bridge and a proper driver too.

Alex

 

[sreerajps]

The transistor in your schematic can only sink current so it can only turn on off the current of the coil, if I understand correctly you want to be able to apply to the coil pulses that change polarity so you will probably need an H bridge and a proper driver too.

Alex

Sorry, consider the transistor in fig. as a TIP122 CBE. So will i need an H bridge and a proper driver too ?

 

[alexan_e]

the transistor as it is can apply pulses to the coil, it will let current flow and it will cutoff the current, the question is what do you want to do.
If you want to be able to reverse the polarity on the coil and not just turn it on/off then you need a bridge.

Alex

 

[sreerajps]

Yes, i need as how an ac signal works on a coil. Yes it changes its polarity. So i need a bridge.. ! Is that what i can conclude. If so give a simple diag with a bridge suitable for this ckt.

The basic need is, a high power oscillator(50V, 2A at least) but ranging 50Hz to 500Hz. adjustable. Can you relate the whole thing and get me something good for me ?

 

[alexan_e]

The bridge with apply (square) wave pulses to the coil, not sinusoidal signals so I hope that this is what you want.
The difficult part is to give you some king of schematic because you need an H bridge and a proper driver that can get your generators signal and then control the four transistors or mosfets, usually this is done with a microcontroller.
Maybe there is an easier solution but I don't have any recommendation.

Alex