microchip

[judejay]

Hello,

Is there a microchip that could be used instead of THAT2252 .

 

[JohnRoberts]

Hello,

Is there a microchip that could be used instead of THAT2252 .

Microchip generally makes MCUs (microprocessors), but they sell some CMOS op amps.

AFAIK they do not make any specialized analog signal processing chips like That corp.

====

It is possible to roll your own RMS level detector using discrete devices. That is generally not worth the trouble these days.

JR

 

[ccaudle]

Hello,

Is there a microchip that could be used instead of THAT2252 .

Many of the available integrated circuit RMS detectors (such as Analog Devices and Texas Instruments) are made for high frequency RF use, not usable for audio applications.
The relevant product page at Analog is here:
https://www.analog.com/en/product-category/rms-to-dc-converters.html

If you mean is there a drop-in replacement with same pinout and same transfer function, then the answer is most likely no.

There is an old application note from National Semiconductor which TI still makes available showing how to make a non-integrated RMS detector with a few op-amps and transistors:
Linear Brief 25, "True RMS detector"

 

[JohnRoberts]

Many of the available integrated circuit RMS detectors (such as Analog Devices and Texas Instruments) are made for high frequency RF use, not usable for audio applications.
The relevant product page at Analog is here:
https://www.analog.com/en/product-category/rms-to-dc-converters.html

If you mean is there a drop-in replacement with same pinout and same transfer function, then the answer is most likely no.

There is an old application note from National Semiconductor which TI still makes available showing how to make a non-integrated RMS detector with a few op-amps and transistors:
Linear Brief 25, "True RMS detector"

yup... Back in the 70/80s whenever I had to do log math, I rolled my own using topology similar to national's linear brief 25. I routinely used cheap transistor arrays (like CA3086) for the multiple matched base-emitter junctions needed. I don't know if these old transistor arrays still exist while if cost is not an object modern high performance dual transistors or quad arrays could be used.

Today just using a dedicated off the shelf part makes sense.

JR

 

[Matador]

Many small 8-bit MCU's can do the math necessary provided they have a few ADC pins. Check this for equations.

 

[judejay]

Thank to all , I can already see there is a wealth of knowledge here!

 

[user 133392]

You can use the RMS detector in the surface mount THAT4305 or THAT4316 to functionally replace a THAT2252 8 pin SIP.
Both devices are current input. (The low supply voltage 4316 can still be used in +/-15V circuits to detect RMS levels far higher than its supply.)

Alternatively you can make them out of transistor arrays as shown here: https://www.proaudiodesignforum.com/forum/php/viewtopic.php?t=856

Or here: https://www.proaudiodesignforum.com/forum/php/viewtopic.php?p=17728#p17728

The later is a better example than the ones preceding it in the thread and shows True Power Summing.

 

[judejay]

You can use the RMS detector in the surface mount THAT4305 or THAT4316 to functionally replace a THAT2252 8 pin SIP.
Both devices are current input. (The low supply voltage 4316 can still be used in +/-15V circuits to detect RMS levels far higher than its supply.)

Alternatively you can make them out of transistor arrays as shown here: https://www.proaudiodesignforum.com/forum/php/viewtopic.php?t=856

Or here: https://www.proaudiodesignforum.com/forum/php/viewtopic.php?p=17728#p17728

The later is a better example than the ones preceding it in the thread and shows True Power Summing.

Alright . Thanks

 

[user 133392]

There's also an example of a 4305 companding RMS detector which has about a 90 dB DR. https://www.proaudiodesignforum.com/forum/php/viewtopic.php?p=17023#p17023

 

[JohnRoberts]

You can use the RMS detector in the surface mount THAT4305 or THAT4316 to functionally replace a THAT2252 8 pin SIP.
Both devices are current input. (The low supply voltage 4316 can still be used in +/-15V circuits to detect RMS levels far higher than its supply.)

Alternatively you can make them out of transistor arrays as shown here: https://www.proaudiodesignforum.com/forum/php/viewtopic.php?t=856

I see a copy of my old TS-1 schematic.

(Interesting that my old schematic has your URL embedded into it, but you are hosting it on your website.)

That circuit is an example of my use of cheap transistor arrays (like CA3086) for precision rectification and even log conversion. I did an exotic log voltage to sawtooth waveform to feed into a digital counter, to read out signal level in dBs.

Later I considered putting a decent VCA or gain cell in front of that rectifier to increase the meter's input dynamic range with a 2:1 compressor. It did OK for what it was 1:1.

JR

Or here: https://www.proaudiodesignforum.com/forum/php/viewtopic.php?p=17728#p17728

The later is a better example than the ones preceding it in the thread and shows True Power Summing.