I am looking for a level shifter circuit, that can convert 5V to 50V logic. I've been looking through some designs. I see a lot of designs uses a current mirror for this. And was wondering, what is the advantage of using a current mirror type level shifter as opposed to a more "easy way" like double npn inverting logic, or npn-pnp level shifter?

Best regards!

  • \$\begingroup\$ What are the output thresholds on the 5V logic, in particular V_OH(min)? \$\endgroup\$ – Ignacio Vazquez-Abrams Dec 6 '14 at 19:08
  • \$\begingroup\$ And what speed do you need? \$\endgroup\$ – WhatRoughBeast Dec 6 '14 at 19:30
  • \$\begingroup\$ @IgnacioVazquez-Abrams V_OH=4.2V,V_OL=0.7V \$\endgroup\$ – Golaž Dec 7 '14 at 13:43
  • \$\begingroup\$ @WhatRoughBeast speed of around 30-50kHz. \$\endgroup\$ – Golaž Dec 7 '14 at 13:45
  • \$\begingroup\$ While I really am looking for a level shifter that will suit my needs, I also want to know the anwser to a question in my post. \$\endgroup\$ – Golaž Dec 7 '14 at 13:46

There is a simple circuit design technique that you can use for a 5V to high voltage level shifter that eliminates a need to provide a separate drive to the upper transistor in the driver. This also uses NPN transistors for both the upper and lower level driver. This works as long as you are OK with the output not pulling fully to GND.

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The way this works is that when the lower NPN turns on current from the load passes through the diode. This puts a forward bias on the diode which in turn reverse biases the BE junction of the upper transistor thus snapping it off whenever there is either load current or residual through current in the upper transistor.

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