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TLV4112: Regulated power supply to op amps?

Abdelrhman Mohamed
Prodigy 40 points
Part Number: TLV4112
Other Parts Discussed in Thread: TLV1171, LM2991, TPS795

I am not sure if this is a simple question (I am not very experienced with electronics).

I want to use the TLV4112 op amp in a circuit where it is going to pass high current >+/-300mA. 

In the circuit design, I already have LDO linear voltage regulators with +5V 1A, and -5V 1A. Since TLV4112 only handles 6V max, I need to reduce this power. Is it possible to use a voltage divider (2x 1Mohm resistors) to get to +/-2.5V and use that directly as power input to TLV4112. I am not sure since I don't know the input impedance of this part.

Do I need a voltage follower as a middle stage? Or do I need two other linear voltage regulators to go to +/-2.5V?

If so, could you recommend any LDO that will supply enough current at +/-2.5V? I found (Texas Instruments TLV1171 1A positive voltage regulator), and (Linear Technology LT3015 1.5A negative voltage regulator), but these seem like an overkill for this.

Thank you very much in advance

  • 0
    TI__Guru* 93105 points

    Hello Abdelrhman,

    The TLV4112 can be powered by either a single supply such as +5 V/0 V, or a dual supply such as +2.5 V/-2.5 V. The supply voltage would have to be established such that the voltage from the VDD pin to the GND pin does not exceed 6 V. The op amp could be connected as a buffer (output tied to the inverting input) and the common point between two divider resistors connected to the non-inverting input. The divider would be connected between the VDD and GND pins to establish a particular input/output voltage level. The TLV4112 has CMOS inputs so the input impedance is extremely high. The divider resistance can be made very high, but keep in mind that resistor noise increases as the value is increased. Keep in mind that adding a large capacitor from the op amp output to ground can result in instability. See datasheet section on page 12 - driving a capacitive load, and Figure 17 for more information. 

    The TLV4112 is capable of current in the range of +/-200 to +/-300 mA, depending on the supply levels. However, it has limited power dissipation and attention must be paid to the PowerPad design considerations on datasheet pages 14 through 16, and in Figure 31 - the Maximum Power Dissipation vs Free-Air Temperature graph.

    Some possible choices for the +2.5 V and -2.5 V regulators are the TPS795 and LM2991, respectively.

    Regards, Thomas

    Precision Amplifiers Applications Engineering