TL972: spec check

GARETH OU

Part Number: TL972
Other Parts Discussed in Thread: LM358, LT1013, TLV2376, TLV2333, LM358BA

Customers use TL972IDR For non-reverse amplification, the action is normal when using dual power supply V+=5V, V-=-5V (The voltage increases with the increase of my VIN)

But switch to a single power supply V+=5V, when V-=0V, the output is always 5V Is there a problem where it is used?

over 2 years ago

0 Ron Michallick over 2 years ago

TI__Guru*** 140136 points

Hello Gareth,

The input stage of TL972 is not rail to rail. I suspect your input common mode is 0V. This is fine with supply -5V,+5V. It is not good for supply 0V,5V

0 GARETH OU over 2 years ago in reply to Ron Michallick

Mastermind 8835 points

Hi Ron

Customers currently test to lower the magnification (magnification: 2 times), the input 1-2V output has a magnification change

Is it because of this parameter?

If you can help me find one set of single power supply or two sets of OPs

I input close to 0V-20mV can be amplified

I have tried LM358 0-3mV, there is no change

Are there any other suggested products?

0 Caro Walter over 2 years ago in reply to GARETH OU

TI__Genius 17587 points

Hey Gareth,

Please post a schematic of your current setup.

All the best,
Carolina

0 GARETH OU over 2 years ago in reply to Caro Walter

Mastermind 8835 points

Hi Caro

The picture below shows the tested schematic Currently (VIN+)-(VIN-) is 5V from 0mV input to 30mV output

0 Ron Michallick over 2 years ago in reply to GARETH OU

TI__Guru*** 140136 points

Gareth,

If input signal full scale is 30mV then you need amplifier with an input offset error less than 0.3mV (1% of full scale)

https://www.ti.com/amplifier-circuit/op-amps/precision/products.html#p3318=10000;1258042&p480=2;2&p2max=0.0015;0.3&sort=p1130;asc

For low cost , optimized for 5V (and lower), and availability, I suggest TLV2376 (faster) or TLV2333 (lower IQ). Almost all dual op amps have the same pinout (for most packages). LT1013 is an exception.

0 GARETH OU over 2 years ago in reply to Ron Michallick

Mastermind 8835 points

Hi Ron

Thank you very much for your suggestions

Can the input offset voltage be adjusted by correction? Because you recommend these two OPs, they should be one-level higher than the original TL972 I used. The customer changed to a single power supply for COST DOWN But this OP is twice as expensive Can you help me find VCM's (V-)-0.1 or above Just find the input offset voltage about mV first

0 Ron Michallick over 2 years ago in reply to GARETH OU

TI__Guru*** 140136 points

Gareth,

For offset correction (post amplifier, usually software), it is important that offset won't cause the output to reach maximum (VOL or VOH)

So I lowered gain to 133 and output minimum is raised to 0.415V.

A 3mV op amp offset will change the output by +/-3mV * 133 = +/-399mV

So output could be range between 415mV - 399mV = 16mV to 4.403 + 399mV = 4.802V

Summary for circuit #2, [A, C, V, RF, RG] solution, no [B, RH, VREF]
Parameter	Real Values	Units	Note
A	165	Ω	Make Standard R choice

C	264,000	Ω	Make Standard R choice
V	5	Volt
RF	264,000	Ω	Make Standard R choice
RG	2,000	Ω	Make Standard R choice


Summary result	Point 1	Point 2	Units
VIN	0	0.03	Volt
VOUT	0.415	4.403	Volt
VCM	0.003	0.033	Volt

This example could use LM358BA if the output doesn't have to sink current from VOUT load.

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TL972: spec check