Voltage Level Shifter

[lmartinez]

Hello everyone,

I would like to know if anyone can help me understand how the voltage level shifter works for the attached circuit. I found it in one of the forum posts. I am looking for a level shifter that can function at speeds of up to 500kHz. It will be driven by a micro controller with a square wave output of 5 volts peak. As a result, i am looking at the attached circuit. Please advise and thank you in advance.

[silvrstring]

Do you have to use that particular design? It's much easier to explain and understand a voltage level shifter made with an opamp.

[lmartinez]

Originally Posted by silvrstring

Do you have to use that particular design? It's much easier to explain and understand a voltage level shifter made with an opamp.

A high speed Operational Amplifier would be great! Please advice

[tibbles]

hi martinez, while silvrstring is getting back,
re your original circuit, im fairly new but i think q2 is actually the "level shifter", but in this configuration it will also invert the signal, so q1 is used as another invertor to maintain the logic.
the diode keeping 12volt from preceeding stages?
but i have been wrong....

[Ron H]

Originally Posted by lmartinez

Hello everyone,

I would like to know if anyone can help me understand how the voltage level shifter works for the attached circuit. I found it in one of the forum posts. I am looking for a level shifter that can function at speeds of up to 500kHz. It will be driven by a micro controller with a square wave output of 5 volts peak. As a result, i am looking at the attached circuit. Please advise and thank you in advance.

What output levels are you looking for? What will the load be?

[lmartinez]

Originally Posted by Ron H

What output levels are you looking for? What will the load be?

The input voltage to the level shifter is 5 volts dc( to consumed less than 20mAmps) and the output voltage is to be 12 Volts DC. The input resistance of the load connected to the Voltage Level Shifter is to be in the range of mega ohms(an op amp buffer). Those are the parameters which I will be working with. PLEASE ADVICE.....

[Ron H]

Originally Posted by lmartinez

The input voltage to the level shifter is 5 volts dc( to consumed less than 20mAmps) and the output voltage is to be 12 Volts DC. The input resistance of the load connected to the Voltage Level Shifter is to be in the range of mega ohms(an op amp buffer). Those are the parameters which I will be working with. PLEASE ADVICE.....

Is your input a logic signal, with 0 volts and 5 volts as the two logic levels? If so, do you want the corresponding output levels to be 0 volts and 12 volts?
The circuit you posted will not do that.

[lmartinez]

Originally Posted by Ron H

Is your input a logic signal, with 0 volts and 5 volts as the two logic levels? If so, do you want the corresponding output levels to be 0 volts and 12 volts?
The circuit you posted will not do that.

Yes, those are the two logic levels for the input and output voltages I would like have.

What if I do not use Q3 and R4 and take the output voltage at the transistor's, Q2, collector? Will that work? Will the circuit I posted function properly at switching frequencies of 500Khz? If not, can you provide a circuit which will do what I am looking for.. Thank you

[MikeML]

Does one end of the external load have to be grounded? If yes, you need a high-side driver.

Is the load capacitive in nature? If yes, you need a push-pull driver to both charge and discharge the capacitance.

[Ron H]

What is your actual application? Why do you need an op amp buffer? If you do, why can't you just use a buffer with gain=2.4?
Post a schematic (a block for the level shifter will be sufficient), and include the op amp buffer, and whatever else is downstream from it.