Need help? HT9170 OUTPUT DV PIN 15

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Which option would work the best.And give me the best out come for my needs.
Your posted audio circuit using the TL972 from TI.Or the tiny LMV1012-25 2-wire preamp chip from Texas instruments.
Assuming I could get them soldered. How would they be connected in series.Please post a diagram if you may.
On how they would be connect together.I'm assuming from output of the first IC to the input of the second IC.
but? What would go in between the first and second ICs a resistor or capacitor or both.
I wouldn't know?
 

You already know how to make a gain of 10 in the DTMF chip from post #7. Except use a trimpot on Rin , to change gain from 10 to 100 by R ratio of feedback to input using 10-100K input and 1M feedback.

The AC coupled input is the same cap on output of 2 or 3 wire mic with builtin fixed 25 dB OpAmp.

The mic is only $0.37@1k and no need to open up!


But in regards to your original question. Connect Red LED direct to DV pin.

Does this answer your questions in this thread?
Is this a serious design for production? Or a DIY 1shot proto?
 

Sorry, I was wrong.
The LMV1012 and LMV1032 cannot be added to an existing electret mic because they are designed to replace the Jfet inside the mic. Use a TL971 opamp instead that is in a small surface-mount package that can be soldered by hand.
 

Audioguru said:
Sorry, I was wrong.
The LMV1012 and LMV1032 cannot be added to an existing electret mic because they are designed to replace the Jfet inside the mic. Use a TL971 opamp instead that is in a small surface-mount package that can be soldered by hand.
Click to expand...

I thought I illustrated that both are already electret Mic's with builtin OA , so no external OA is required.

But I was wrong in saying most electrets available are noise-cancelling.(that was just my experience based on packaged offerings) As these are omni-directional as well and need to be focused.
 

SunnySkyguy said:
I thought I illustrated that both are already electret Mic's with builtin OA , so no external OA is required.
Click to expand...
Texas Instruments make the IC and show how it is connected for manufacturers of electret mics, they do not make the mic with one inside. I do not know of any electret mic available that has one of these ICs inside replacing the Jfet that is usually used.

Remember the old now obsolete LM3909 LED flasher IC? It was made for manufacturers of flashlights but the IC manufacturer did not make the flashlights. I never saw a flashlight made with that IC inside flashing an LED.
 

Sunnyskyguy

Does this answer your questions in this thread?
Is this a serious design for production? Or a DIY 1shot proto?
Click to expand...

Its a DIY 1shot proto. At this time IN this project.

The HT9170 CAN NOT give a gain of 100. Maximum gain is 30 there would be clipping if the
gain is above 30.look At the datasheet.

I need a diagram on the components use for the op amp and how to set the amp up
I might of misunderstood you on this post.
 
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Avo spec is 65dB gain that is >1000 on p.4

good luck
 

Audioguru

I may need a gain of 1000.But not sure? Until I build the circuit and do testing you post in #17
What is the max (gain) that this circuit can provide.And what is the operating current for your circuit.
 

The input opamp of the HT9170 decoder can provide gain. Its fT is 1.5MHz so its gain at 15kHz is 100 but its datasheet shows only a gain of 1 so it might be noisy. Try it with a gain of 10.

The TL971 opamp has plenty of high frequency gain but its maximum gain is only 1000. try it with a gain of 100.
 

Audioguru and Sunnyskyguy This question is both.

Looking for best Mic on a budget.
Can you tell me?If you both were on a budget.As I'am.Which condenser electret microphone cupsule would you use.Recommended from digikey.com . buy here.
 

I use electret mics from wired telephones, cordless telephones, cell phones, intercom systems and toys. They all worked about the same and cost me absolutely nothing.

Radio Shack sells one that is fine for three dollars but it is worth only one dollar. Maybe they bought the $.96 ones from Digikey.
 

Audioguru


The output of the TL971 there's the 0.33uF cap that get connect to the input on the
HT9170. The 0.1 cap that's connected to pin2. I want to know do I keep that cap tied
to the resistor or does it need to be deleted. Want to make sure.


Also I need to use the TL972 the TL971 does not come in a plastic dip 8pin package for breadboarding.
will the TL972 be Ok to use in the amp circuit.
 

The 1uF capacitor C2 in my mic preamp schematic is needed to allow high AC gain but no DC gain. If it has DC gain then it will amplify the 4.5V bias voltage causing its output to be continuously saturated as high as it can go.

I think the high capacitance between rows of contacts and wires all over the place on a solderless breadboard will cause a high frequency opamp like the TL972 or TL071 in this high gain circuit to oscillate at a very high frequency instead of amplifying audio.
When you use only one opamp of a dual then the unused opamp must be properly disabled.

A low frequency lousy old opamp like an LM741, LM358 or LM324 might work on a breadboard.

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Maybe you are asking about the 0.1uf input coupling capacitor at pin 2 of the DTMF decoder IC? I hope you are using the circuit version 1 in the datasheet and not the circuit with a differential input.
Then the 0.1uF capacitor is the same capacitor as the 330nF output capacitor in my mic preamp circuit. Use only 1 capacitor. Its value is calculated to pass the lowest DTMF frequency of about 300Hz into its input resistor that is 100k ohms. So a capacitor value of 0.01uF to 0.1uF is fine.
 

if you have ever heard the dit-dity-dit sound from an external electret mic when a cell phone is nearby, that due to,lack of a <100pF cap in shunt with std decoupling caps or,lack of good CM ferrite choke for GHz RFI.. So,I would include that. Cell phone transmit this pattern on a regular basis to get the strongest nearby towers for roaming.
 

AG
The 1uF capacitor C2 in my mic preamp schematic is needed to allow high AC gain but no DC gain. If it has DC gain then it will amplify the 4.5V bias voltage causing its output to be continuously saturated as high as it can go.
Click to expand...

No? Not the 1uF capacitor in your op amp circuit.

The 0.1UF input coupling capacitor connected to resistor 10K in the HT9170 circuit.Should I remove that 0.1 cap> went I connect the output with the 0.33uF to the input on pin2 of the HT9170. So just use one capactor.



AG
If I use the dual TL972. How do I properly disabled one of the amps.Then just use the other amp. Or are the two amps internally connected.I assuming there not.

Then your telling me i need to solder the circuit on a protoboard for your circuit to work.Using the TL972.

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How and where would i included the 100pF in stunt with the std decoupling caps please show on circuit,And a CM ferrite choke. Please show me where to put it and how and what the value i need to use.
 

cybertron said:
How and where would i included the 100pF in stunt with the std decoupling caps please show on circuit,And a CM ferrite choke. Please show me where to put it and how and what the value i need to use.
Click to expand...

The mic cable acts as antenna to EMI including cell phone roaming checks. The mic will not amplify but the non-linear effects of Amplifier signals wll rectify the carrier and that is what is heard. You would apply a SMD or disc with very short leads on any high gain input across audio. amplifier inputs. CM chokes are commonly used on Desktop mic cables, laplotop DC charger cables and VGA cables. Selection requires salvage or a catalog.
 

The TL972 dual opamp works at radio frequencies so I think the capacitance of the contacts and wiring on a solderless breadboard will cause it to oscillate. It depends on your layout and wiring. The same for a soldered circuit.
Any opamp that works fine with a gain of 1 can be disabled like this:
 

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  • The TL972 has a gain BW product of 12 MHz with a 100pF , 1k load.
  • even if you have very inductive long wires, it will not oscillate under these conditions with proper decoupling within 1" of the chip.
  • even better, when high gain is used, such as x240, the BW is reduced to 50kHz and the only thing that can detect from a >1GHz cell phone on the wires is input diode which can only rectifying some of the carrier and amplifiying the envelope.
  • avoiding this pickup requires 50 to 100 pF across the +/- input within 1" of the chip.
  • using twisted pair and/or shielded wire for the mic improves immunity from RFI even more.
  • the most unstable mode of any Op Amp is the unity gain, but this is not required for this application, even on a solderless board.
 


So? If I use one amp side of the TL972 for the circuit in post #17.Then disable the second amp as your attach circuit in post #38. Correct?
 

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