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Adjustable Voltage Regulator - TLV1117

Karthik rajagopal

May 9, 2016
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Hi all,
Recently while referring to TLV1117 adjustable voltage regulator from Texas Instruments, I came across its functional block diagram. Functional block TLV1117.jpg

The following questions came up to mind with regards to its working:
1. The package has only 3 pins among which none connects directly to ground. Then how is the internal op-amp powered?

2. If the op-amp is powered by the potential difference between its output and input, then how will it get powered ON initially since the op amp controls the BJT that connects the input to the output?
Datasheet: https://www.ti.com/document-viewer/TLV1117/datasheet/abstract#SLVS2972356

Any related documents would also be helpful.
Thanks in advance.
 

Harald Kapp

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As the datasheet states, this is a simplified schematic. Don't trust on such a schematic to reveal the inner circuit of the chip.
Then how is the internal op-amp powered?
BY the voltage differential between input and output (>= 1 V required).
how will it get powered ON initially since the op amp controls the BJT that connects the input to the output?
Have you noticed the 5 mA current source in parallel to the transistor?
 

Karthik rajagopal

May 9, 2016
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As the datasheet states, this is a simplified schematic. Don't trust on such a schematic to reveal the inner circuit of the chip.

BY the voltage differential between input and output (>= 1 V required).

Have you noticed the 5 mA current source in parallel to the transistor?
Thanks for the reply.
 
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