OPA172: i need to convert 4 input current to 4 output current is it possible .

Hi Ritesh,

Are you planning on using a sense resistor to convert the input current into a differential voltage? Howland current pumps used for voltage to current conversion, hence why you would likely need to convert the input current to a voltage. 

Best Regards,

Robert Clifton

Ritesh,

This is a very low gain and huge output offset. This will require a very accurate offset.  This seems to be a very odd request, could there be a different solution? Is the output current floating? What is the voltage compliance range for IIN and IOUT.

Hi Robert sir , 

Basically I need this circuit to select frequency, this require current used to select frequency in YIG Filter .

Now a problem arrive in my project where we are using new YIG Filter which require 503-519mA and +5v but our external current which is 350-0mA remain same to be use in project . 

So we need some circuit ,which map one to one current  . But I don't know how to do it . 

Hi Ron sir , 

Basically I need this circuit to select frequency, this require current used to select frequency in YIG Filter .

Now a problem arrive in my project where we are using new YIG Filter which require 503-519mA and +5v but our external current which is 350-0mA remain same to be use in project . 

So we need some circuit ,which map one to one current . But I don't know how to do it . 

Hi Robert sir , 

Basically I need this circuit to select frequency, this require current used to select frequency in YIG Filter .

Now a problem arrive in my project where we are using new YIG Filter which require 503-519mA and +5v but our external current which is 350-0mA remain same to be use in project . 

So we need some circuit ,which map one to one current  . But I don't know how to do it . 

Hi Robert sir , 

Basically I need this circuit to select frequency, this require current used to select frequency in YIG Filter .

Now a problem arrive in my project where we are using new YIG Filter which require 503-519mA and +5v but our external current which is 350-0mA remain same to be use in project . 

So we need some circuit ,which map one to one current  . But I don't know how to do it . 

Hi Ron sir , 

Basically I need this circuit to select frequency, this require current used to select frequency in YIG Filter .

Now a problem arrive in my project where we are using new YIG Filter which require 503-519mA and +5v but our external current which is 350-0mA remain same to be use in project . 

So we need some circuit ,which map one to one current . But I don't know how to do it 

Would something like this work?  The power source and return side of current sharing a node?

What is the voltage compliance range for IIN?  So we can size RIN

What is the minimum and maximum range for YIG DC resistance? So we know what PWR voltage must be.

Is the tuning closed loop such that the input current changes to fine tune the output current?

Hi sir ,

yes  power source and return side of current sharing a node we exactly looking for this type .

point -1 = voltage compliance range for IIN is 5V (we have tested in old YIG)

point -2 = minimum and maximum range for YIG DC resistance is 8 ohm 

point 3 = yes , it is closed loop , we need output current in the range of 500mA from lower current vary from 0 to 350mA .

means no current at input side give rise to 519mA at output ,117mA at input give rise to 513mA at output.

This draft solution is close to the original request. Convert [350mA,0mA] into [503mA,519mA]

Key considerations are:

T1 needs to be a power transistor, 2N3904 is not recommended.  If YIG is shorted, T1 will see 6 watts of power.

R5, R6, R12, R13,R14, R15 need to be better than 1% because they are critical to the high offset current. 

OP1,2 need to have low Vos specification because Iout error is about 2uA/uV of Vos error. TL4051B12 is a 1.225V shunt regulator

Howland current pumps need good resistor matching for good accuracy. Ratio of R15/[R1, R2, R14] being equal to R12/[R4,R5,56]

Current gain scaling is inverse to R13 

I think a better solution is to let the [350mA,0mA] input current change output current more, for example [460mA, 560mA].  This is better if this circuit is not the critical part (the error amplifier) of the closed loop.  The loop will have a smaller swing for IIN and the loop will compensate for offset error of this circuit using the "extra" range of IIN.

For example if one system has an output range of [430mA, 530mA] and another system is [490mA, 590mA]. In both cases the closed loop can create [503mA, 519mA] output. 

Could the system's closed loop accept such a solution?

I wasn't happy with the need for so much resistor matching. Therefore, I changed the circuit topology to level shifter (N1, from low supply rail to upper rail to reduce matching complexity. 

In this version, the key considerations are: R2, R4, R8, OPA1 Vos which set the high offset current magnitude. This is smaller list than the previous solution. N1 should have low off leakage.

Hi Sir,

Thanks for the Level shifter topology circuit . we are working on it to implement it ,

can you please share following technical information to clear doubt .

1. TL4051B12 is a 1.225V shunt regulator is placed in series ,what is effect of it .

2. IOP1,IOP2 ,N1 and P1 manufacturing part no. preferred smd component can you suggest .

3. can you share Simulation result for all 4 input current if possible .

1) It generates a voltage that is negative relative to VCC. R2 and R4 scale that to VCC - 0.519V (for a base output of 519mV/R8 = 519mA) ; R6 supplies bias current to run TL4051B1

2) IOP1 = OPA4186 very low Vos error. IOP2 =same or save money TLV9104

2) N1 low power, >16V, low Ioff ; if you find one, I'll check out the data sheet.

2) P1 high power package with heat sink (can be PCB heat sink) ; you could lower VCC to reduce heat in P1 (9V would be cooler)

3) 

TI Tina circuit 

350mA,0mA to 503mA,519mA offset ground shift.TSC

I just created BOM with Manufacturing part no. can you just confirm can I continue with this part mostly P1 and N1.

some of the doubt are ,

1. Wattage requirement of R1,R2, R4, R8 .

The original request was 4 in 4 out, so four identical circuits? If yes, quantities (other than IOP1,2) will be 4 times.

C1 doesn't have to be 1% , even 10% would be fine. 

R1 should be 2 watt for margin and 1% is fine. R3 can be 1% and low wattage 

R4, R5 can be low wattage.

R6 can be 1% low wattage.

R8 should be 1/2 watt for margin

R9 can be low wattage. 

P1 needs a much bigger package with a thermal tab (heat sink tab)

N1 needs to be change to NMOS. The part number now is PMOS

In layout, R1 and R8 need a kelvin connection. 

we want 1 circuit , 4 different current input and 4 mapped different current .

1 . can i used R=14.7K//14.7K ,0603,0.1W, to have 7.35K ?

2 . following are updated BOM is it ok sir?

Yes, that 14.7k combination is fine 

N1 2N7002 and change R5 to 1k and R9 to 220k (I couldn't find a low enough specified off current NFET)

P1 SIA469DJ-T1-GE3 or almost anything here: https://www.digikey.com/en/products/filter/transistors/fets-mosfets/single-fets-mosfets/278?s=N4IgjCBcoGwAwyqAxlAZgQwDYGcCmANCAPZQDaIAzABwCsYclIAukQA4AuUIAyhwE4BLAHYBzEAF8iYMAHYALEhCpImXIRLlwYGLRiJpOvbJBEAnNWowT0xrpvg7e0yGpnKMl9QBM3qy79KILgXWVpvWgQAmDNZOGpo6lk6RLNaRSI-MBomTPT07wD6M3kMkAiweTgIPJ14IqMEon04NJry6xhvMwDKeTAI3tb5HsyR-QNy8fqxs11RqbnaJsX7APH09bmRrZh5Se9x%2BULZmEoHQ7nKWl2-AIYkhYUwNzLvB7D7%2BNlckBgfbYBBDef5ArozcpwdKWIHpWQXPx0BbWSqxFwoyLtF5wd4ncCydybaQEvrIqqRZGySrUMpydxVdFU%2BghYnubws-HuAYsdhcSC8AQicRSSGg6DKdDYfBEUiQCjsgAEADUXJQ4MrVbQNUQaNqQFU9fItSqiLRjej1SrWCBONwAKrCQQcADyaAAsngMDgAK78PCSIgAWkK4pUAm9GllFBu5hYEhFiHFggAJtxAwx2rb%2BS4OABPNj%2B-le1DxoA

Dear sir,

can you please check attached layout . 

MPK-LEVEL-SHIFTER-1-0.PDF

Also add a100nF bypass capacitor for op amp pins 4 to 11.

Because you use only 2 op amps OPA2186 can be used. 

MPL-LEVEL-SHIFTER-1-0-100424.PDF

Dear Sir

PFA updated Layout as recommended .

let me know is it good 

Dear sir,

we are getting output  as below,

1 . P1 = PMV65XP,225 used rest all component are same .

i had set +12V/550mA right now ,

IOUT = 550mA getting with +12V down to 7.45V 

can you please help to troubleshoot problem .

Tapajit,

Are you saying your supply voltage was set to 12V with a 550mA clamp and the result was 550mA and supply automatically reduced to 7.45V?

I suggest start testing without any load on the output. I would expect the current to be vastly lower. If not lower, carefully feel for which components are hot. 

If current is low, vary the input current and measure all node voltages. You can verify all is working except for IOUT. If any node voltage has an unexpected DC or any AC voltage, debug that. Let me know results of the open load testing.

Dear Sir,

I  earlier added P1 reverse means source and Drain are interchanged but when correction done following i got ,

open load test look OK no Current consumption .

1. on VCC = +12V ,we are getting 222mA with IIN = 0mA

2. when IIN = 117mA , IOUT = 214mA

3. when IIN = 234mA ,IOUT = 209mA

4. when IIN = 350mA , IOUT =202mA

just P1 =PMV65XP,225 heating up .

just need to increase current to required level .

Tapaji,

You are making progress. Let us continue next step, right current for VIN = 0mA

I was going to show the nodes to measured when I noticed this. It is upside down. As drawn, it acts like a diode, 0.7V. 

Put pin 1 on top and pin 2 on bottom, then it will be a Zener shunt 1.225V 

From the pinout , I assume you have fixed shunt (two active pins) seen below. 

After changing above, check the output current, if correct then continue testing other input currents.

Otherwise measure the voltage at red nodes.

Dear Sir,

just reversed D1= TLV4051 source and drain , and we are getting D1 nodal voltage as 10.77V .

and IOUT reached to 470mA .

1. firstly P1 = PMV65XP,225 is heating up .,how much rated power MOSFET required .

2. following attached nod voltage observed with no load .

Tapajit,

When IOUT was 470mA what was the voltage across these two green nodes? The kelvin sense voltage. It should be 519mV.  

1) Power equation is IOUT[i] * (12V - 1ohm * IOUT[i] - IOUT[v]) 

2) The D1 voltage reference and the resistor divider to op amp are working well now. 

Dear Sir,

Thank you for the support , using P1=IRFL9110TRPBF , we are finally getting expected current .

voltage measure at E1 = 11.95V and E2 = 11.43V .

just PMOSFET selection remaining . can I select greater than 5W power rating of it . 

Dear Ron sir ,

1. Can I use P1=IRFL9110TRPBF  ?

2. What parameter required for selection PMOS ?

Hello Tapajit, 

Ron is out on vacation. I will continue support here. 
Could you please share what the most up to date schematic looks like? 

All the best,
Carolina

Hi Caro Walter ,

original Schematic is same given by Ron sir , i am attaching it ,

i am need basic knowledge how much power rating required min. for P1 = PMOSFET .

7041.350mA,0mA to 503mA,519mA offset ground shift.TSC

Dear Sir,

can i used P1 = NTF6P02T3G 

Dear sir,

i just used 

Tapajit,

You need to determine which aspect(s) of the circuit are supply voltage sensitive. 

Measure R2 (put both DMM probes on R2) voltage at different supply voltages. 

Measure P1 VDS (put both DMM probes on P1 drain and source) voltage at different supply voltages. 

Measure P1 VGS (put both DMM probes on P1 gate and source) voltage at different supply voltages. 

Measure R8 (put both DMM probes on R8) voltage at different supply voltages.

Dear Ron sir ,

But P1 =  NTF6P02T3G is good choice for this design?

Tapajit,

That transistor looks good to me.

Dear Sir,

PFA voltage at component . ,

at 9V P1 heating little bit  but at +12V it is heating more .

Tapajit.

Op amp IOP1 is not fully correcting for supply drop. Perhaps N1 is starting to conduct some current. Check voltage across R9 and gate voltage for N1.

Tapajit Mondal said:

Basically I need this circuit to select frequency, this require current used to select frequency in YIG Filter .

Now a problem arrive in my project where we are using new YIG Filter which require 503-519mA and +5v but our external current which is 350-0mA remain same to be use in project . 

Did this circuit solve your original problem?

Dear Sir,

PFA required reading ,

Tapajit,

The image above was already in the thread. Was this supposed to be a different data table?

yes sir 

i had just calculated voltage at R9 and N1.

Tapajit,

The numbers look good. This may be as good as it gets.