# binary to thermometric conversion

Discussion in 'The Projects Forum' started by vikkie, Jan 9, 2009.

1. ### vikkie Thread Starter New Member

Dec 20, 2008
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Hi,
I want to design a 4-16 decoder implementing thermometric code.I would appreciate it if anyone tell me how to do this at transistor level.

2. ### Alberto Active Member

Nov 7, 2008
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CD4067 is a pretty old 5 Volts TTL integrated IC that decode 4 to 16 lines. You should find it using google.

Alberto

3. ### KMoffett AAC Fanatic!

Dec 19, 2007
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CD4067 is CMOS not TTL.

Ken

4. ### Bernard AAC Fanatic!

Aug 7, 2008
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I Googled " thermometric code " and found more than wished for, except for a definition . Another 4 line[ non thermo.. ] decoder is 24 pin CMOS ,4515.

5. ### beenthere Retired Moderator

Apr 20, 2004
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Hey vikkie - can you help us out with a quickie definition of thermometric code?

6. ### KL7AJ Senior Member

Nov 4, 2008
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Thermometric code is simply binary code where each digit has the same place value. If you have a string of comparators, such as in a flash a/d converter, what you get out is thermometric code.

Eric

7. ### duffy Active Member

Dec 29, 2008
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Thermometric = unary

00 = 000
01 = 001
10 = 011
11 = 111

Apr 20, 2004
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Thank you.

9. ### vikkie Thread Starter New Member

Dec 20, 2008
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Thanx for the response.Actually i have to design it using CMOS transistors.I cannot use a built-in decoder.i want to know the design technique for this decoder

10. ### Bernard AAC Fanatic!

Aug 7, 2008
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Are CMOS transistors available? Are CMOS inverters allowed, such as 74C04 & 4009 with open drain,ea. 6 per chip?

11. ### Bernard AAC Fanatic!

Aug 7, 2008
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Using duffy's example I came up with this scheme. Uses home built negative nand gates and + nor gates. It would be slow as there is a lot of rippling down. The outputs are inverted.Page was not big enough for 12-15.

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12. ### duffy Active Member

Dec 29, 2008
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Wow, that's going to be well over a hundred transistors. Hope you have a good soldering iron, vickie.

13. ### steveb Senior Member

Jul 3, 2008
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The CD4007 has transistors that can be used directly. There are three matched complemetry pairs. One pair is wired as an inverter, but the other two pairs can be used as transitors for general purpose.

14. ### Bernard AAC Fanatic!

Aug 7, 2008
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If a few pins are strapped together the 4007 gives three CMOS transistors, but how can they be converted into and gates?

15. ### Bernard AAC Fanatic!

Aug 7, 2008
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Who cares. Small error on print, gate 11 out should go to gate in nor's on 10. also ,all1's inputs are paralled,as with 2's 4's & 8's.