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LMP91000: Does LMP91000 works for Alpha-sense PID-A12 sensor which gives output in mv.

March 14, 2018, 6:03 am
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Part Number:LMP91000

Hello All,
        I am new in design(digitize) of the electro-chemical and photo ionization sensors. I checked the datasheet and web-bench for the LMP91000 which is very good and it works for many sensor which output the current per PPM.

        however in my design(with single design and single socket) i need to detect the CO-AF(output in current) sensor and PID-A12(output in mv) sensor from alpha sense. LMP91000 is suitable for the co-af but i am not sure that it will work for the sensor which gives output in mv.

       do i need external circuit to convert the current into the mv or mv to current so that both the sensor work fine with the LMP91000 ?

       Pardon if i missed anything ,Please suggest anything if required.

       Thanks in Advance.

Thanks,
Bhautik

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XTR300: Circuit Configuration Questions

March 14, 2018, 7:23 am
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Part Number:XTR300

Hello,

We have a customer who is asking the following:

"We want use XTR300 for : +-10V , 0 to 10V, 0 to 20 mA , and 4 mA to 20 mA, all configurations  must be controlled  via software .

 

I Question , controlling  +- 10V and , 0 to 10V

                                                                              DRV

                                                                              _|_

                                                                              __   47nF

                                                                               |

          5V-----|LDO  Vout 2.5V|  -------------------•-------------------------àSET (pin4 XTR300)

              ENABLE   ---à |                                  |2,49K Ohms 1%|

                                                                           |

                                                                           |

                                                                         GND

 

         RGAIN  =10K

 

La idea is to Enable-Disable  2.5 V from LDO in order to provide 2.5 V or 0 , depending is VOUT +-10V or +10V.

This is correct  I would like to know if this is correct.

 

II, controlling   4 to 20 mA , and  +- 20 mA

a)      Single ended : Is any effect to be connected  RGAIN ?

b)      Bipolar  can be use the above circuit in order to drive +- 20 mA"

Could someone please have a look?

Thanks,

 

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TINA/Spice/OPA191: Resister calculation

March 14, 2018, 8:00 am
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Part Number:OPA191

Tool/software:TINA-TI or Spice Models

Hi,

In my last post I asked about the resistor values in case my opamp input was between 0 - 4.096V and output ±10V I did the calculations and this was correct.

Last  post: e2e.ti.com/.../670117

Now I want to change the input between 0 - 3.3V and a output of ±10V and TINA doesn't give the ±10V with the same way of calculating the resistors as before. Below picture is from last time.

Transfer function is Vout = Vin * (k1/1+K1) + Vin * (K1*K2/1+K1) - Vref*K2          K1=R2/R1 and K2=Rf/Rin

If I take Vref = 1.65V then k1 = 6.06061 and K2 = 6.06061, but the OpAmp output is between 8.85V

if i take Vref =  1.1V then K1 = 1.50376 and K2 = 9.09091, but then Opamp output is between ±11.96V

Can someone tell me what I'm doing wrong

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OPA320: A question about the "1 MHz, Single-Supply, Photodiode Amplifier Reference Design"

March 14, 2018, 8:13 am
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Part Number:OPA320

Hi all, 

I am reading the "1 MHz, Single-Supply, Photodiode Amplifier Reference Design" application note and have a question about the pole mentioned on Page 5. Why the R in parallel with C gives a pole of 1/2pi*C*R? 

Thanks.

(Please visit the site to view this file)

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LMP7731: Failing units on current sensing application

March 14, 2018, 8:34 am
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Part Number:LMP7731

I am having some issues with this amplifier.

Application: shunt voltage (low resistance 0.05Ohms) differential input amplifier with gain=8. The schematics can be shared if needed.

Symptoms on failing unit:

-              Random or permanent failure on final application

-              Gain variations are observed

-              Input currents are 1000 times bigger than expected by datasheet on IN+

-              Thermal analysis shows temperature variation during failures

-              Power supplies on application (+2.5VDC, -2.5VDC) have been verified

-              During failure mode, I observe power supply consumption variation.

-              One fail component shows a non-linear response (almost constant output) for low input voltages in linear non-inverting configuration. It was compared with a new brand component.

 

Thanks for your support

Roberto

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AMC1100: Transformerless mains sensing using isolated amplifier

March 15, 2018, 1:41 am
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Part Number:AMC1100

Dear Sir,

Following circuit is from "Replacement of input mains transformer in inverter with isolated amplifier".

My question is : Does AMC1100 need differential signal shifted by 2.5V at input side with respect to input side ground ?

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MULTI-CAL-SYSTEM: PGA309 MULTI-CAL-SYSTEM Latest Software

March 15, 2018, 9:08 am
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Part Number:MULTI-CAL-SYSTEM

Hello,

I'm currently running version 2.1 of the PGA309Multi-Cal-System, I've seen forum posts with expired links to version 2.3i, could you please provide me with a link to the software as well as the source code?

Thanks,

Greg

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LM2907-N: Freq to Volt converter in pin 4

March 15, 2018, 9:47 am
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Part Number:LM2907-N

The output that I get at pin 4 & 7 is always 0.3 V. However, when I measured it at pin 3, I get the right result. Can You also check my values for the high and low frequency circuits. (Please visit the site to view this file)

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OPA1612: SoundPlus OPA1612 in replacement of OPA2134

March 16, 2018, 6:12 am
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Part Number:OPA1612

Hi Community, TI!!!

I would like to upgrade an audio amplifier OPA2134 and the TI site web recommands me to change for a new OPA.

I found that OPA1612 was in the ultimate soundplus collection that's why i have change for it.

Unfortunatly with the new OPA1612 I have obtained a lot of noise on the output channel.

I try to use a cheap component like NE5532P, no noise, with OPA2134 no noise with the OPA1612 a lot of noise.

Do you know why i obtained this issue with the new OPA1612?

Thanks a lot

Pierre

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opa350: configurable gain suggestions

March 16, 2018, 12:45 pm
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Part Number:opa350

Hello,

We’re driving a current sensor that has a current source output.  We will be using a range of current sensors with an output range from about +/-100mA to about +/-300mA.  This measured current to a microcontroller ADC.  The circuit needs to be configurable so that we can adjust the scaling based on which current sensor is in use.  The general topology for this will be a current sense resistor followed by a diff-amp. ( I can share schematic offline.) 

The first idea we had for configurable scaling was to use a fixed diff-amp gain and implement selectable sense resistors.  The drawing below shows up to 5 selectable sense resistors.

Note:

(1)    The sense resistors are in the less than 10Ω range so the switch needs to have very small ON resistance.  (seems like 10mOhm is a good value for negligible error)

(2)    Looks like there will be current swings positive and negative, so does the voltage across the sense resistor.  This means that the switches that are opening up the unused paths must be able to block bipolar voltages.  A single MOSFET won’t work because the body diode will conduct during the negative side of the cycle.

The other option was to use a single, one-size-fits-all current sense resistor followed by a variable gain amplifier.

Would you recommend one or the other implementation?
Or have an alternative solution?

Thanks very much, Keith

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THS7319: Driver for 10 MHz Distribution Amplifier

March 18, 2018, 5:59 am
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Part Number:THS7319

I am trying to come up with a design for a 10 MHz distribution amplifier with 50 Ohm input and output.  The design will take input from a GPS-Disciplined Oscillator (GPSDO) or an accurate frequency standard.  Output from my GPSDO is a 1.8 Vpp (into 50 Ohm) 10 MHz sine wave but it has been noted that there are often harmonics present, particularly at 20 MHz so I'd like to include some kind of filtering if possible.  I'd also like to allow for a wider range of inputs going lower down to 1 Vpp but this would be a one off adjustment by the user to suit their particular GPSDO.

The outputs will all drive into test instruments such as frequency counters and oscilloscopes which have 50 Ohm external 10 MHz frequency reference inputs.

The THS7319 seems like an ideal device to drive 3 outputs per IC (with easy to achieve 50 Ohms in/out) but it's only available in 1mm pitch BGA and I'd prefer something with 'legs' like a TSSOP or QFN; I will use the BGA if I have to, it just makes it difficult to build prototypes - I can also use individual devices e.g. SC70 or SOT23-5 but I'd like to keep the cost at or below $1 per output if possible.  I'm designing for (10 ish) multiple outputs so I could put a single filtered buffer amp in as the input stage and then use unfiltered drivers having removed the harmonics in the first stage.

Can you comment on the suitability of the THS7319, help with device selection, or point me to any reference designs that may be suitable for this requirement?

Thanks in advance.

Ted

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AMC1200: AMC1200 output stage status when un-powered

March 18, 2018, 11:05 pm
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Part Number:AMC1200

Hi Team,

Here is South China FAE Sunny, our customer meet some problem on AMC1200 in power up stage, and they have one question: When VDD1 of AMC1200 is powered while VDD2 is un-powered, what status of the output stage of AMC1200? Is it output 0, or high impedance, or unkonw?

this imformatino is quite important for customer to find the issue.

Thanks very much.

Regards, Sunny

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THS7530: About Noise Figure

March 19, 2018, 1:23 am
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Part Number:THS7530

Hi,

Would you tell me why the noise figure specification is difference in a gain setting for Figure 3. of the datasheet?

Best Regards,

Toshiyuki 

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ISO121: Analog signal isolation

March 19, 2018, 4:33 am
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Part Number:ISO121

We have selected ISO121 amplifier for our analog signal isolation. But have a feeling that the amplifier is just not the right fit for our application.

Our application has input voltage range from 0.5V single ended to +/-5V differential input voltage. The analog signals will have input DC offset which I want pass through the isolation amplifier alongwith the AC signal (Sine wave).

Do you have any solution with TI where in I can isolate the analog signal input (which will have 0.5Vpp to 10Vpp)?

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PGA308: Strain gauge amplification of positive and negative VDiff signals

March 19, 2018, 6:05 am
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Part Number:PGA308

Hello,

I'm looking at the PGA308 to amplify a strain gauge on a force sensor. I need to be able to measure both tension and compression forces so my strain gauge will produce both +ve and -ve output signals to the PGA308 inputs.

The gauge is powered from a 3V reference so it's output will be 1.5V with no load (assuming an ideal zero balance). It has a 1mV/V rated output so I will only get a few mV swing around this mid rail voltage.

Before discovering the PGA308 I was designing a traditional load cell amplifier and manual variable gain stage. I was calculating gains of about half what the PGA formulas are suggesting which to me indicates that the PGA308 will only work +ve VDiff voltages (i.e. compression forces only, not tension).

Is this a true limitation of the amplifier or can it work with a strain gauge that can bend in tension and compression and therefore provide +ve and -ve VDiff voltages?

Any help is appreciated.

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INA826: Thermal Issues

March 19, 2018, 7:05 am
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Part Number:INA826

Hello,

I am currently using an INA826 to measure the voltage of a Pt100 Sensor, which is working properly except for the INA 826 overheating after some minutes (>15min). I replaced the destroyed INA an checked again with a thermal camera but its still overheating or at least getting warmer and warmer (>50°C).

My inputs values are listed below:
Supply: +-15 V
Input voltage: ~10 mV
Common-mode voltage: ~2.5 V
Gain resistance: ~100 Ohm (-> Gain: ~500)
INA package: DRG (3x3mm)

I checked the layout for shortcuts and moreover checked the voltage values while using the INA. There were no notivable problems. Does anyone have an idea what could cause the overheating?

I just read in another post, that the thermal pad should be connceted to the negative voltage supply. Mine is currently connected to ground, could that be the reason for overheating?

Kind regards,

Nicolas M.

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XTR111: EF Pin Timing

March 19, 2018, 8:57 am
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Part Number:XTR111

The timing for the EF pin of the XTR111 is not stated in the data sheet. Do we have any information as to how long after an error is sensed before the EF is asserted?

Thanks for your help with this!

Richard Elmquist

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OPA340: Die area needed to predict radiation susceptibility

March 19, 2018, 1:44 pm
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Part Number:OPA340

Do you have radiation data for the OPA340NA? If not,

could you provide the die area? This would be used

to predict susceptibility to space radiation.


Thanks,

Carolyn Sleeper

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INA121: Radiation Data for INA121U

March 19, 2018, 1:46 pm
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Part Number:INA121

Do you have radiation data for the INA121U?

If not, could you provide the die area?

This would be used to predict susceptibility to

radiation.

Thanks,


Carolyn Sleeper

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INA333: Switched Gain Resistors

March 19, 2018, 2:15 pm
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Part Number:INA333

The spec's of the INA333 fit my application well. However, I need to switch between specific gain levels. Apart from adding value and variation to the gain resistor, are there any concerns with muxing between gain resistor values?

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