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Re: Low Noise Transistors: Comparing the ZTX1053A and ZDT1053 (Dual) vs. the ZTX689B and ZTX851

Posted: Tue Mar 17, 2020 10:22 am
by mediatechnology
2SB737: https://ka-electronics.com/shop/index.p ... uct_id=108

I'm not shipping internationally right now due to reduced flights and long mail delays.

But I have them...
Their history: https://proaudiodesignforum.com/forum/p ... =11&t=1195

Re: Low Noise Transistors: Comparing the ZTX789A to the 2SB737

Posted: Tue Mar 17, 2020 11:27 am
by mediatechnology
A comparison of the PNP ZTX789A to the PNP 2SB737.

Image
Low noise transistors. Comparing the ZTX789A (top) to the 2SB737 (bottom).

Re: Low Noise Transistors: Comparing the ZTX1053A and ZDT1053 (Dual) vs. the ZTX689B and ZTX851

Posted: Tue Mar 17, 2020 4:00 pm
by JR.
If only we had these devices back in the day.... :lol:

Oops we did.

JR

PS: BTW I found a partial tube of old panasonic MN3001 BBD chips.... I doubt these are in high demand these days but $15-$20 ea back in the 70s

Re: Low Noise Transistors: Comparing the ZTX1053A and ZDT1053 (Dual) vs. the ZTX689B and ZTX851

Posted: Tue Mar 17, 2020 4:44 pm
by mediatechnology
JR. wrote:
Tue Mar 17, 2020 4:00 pm
If only we had these devices back in the day.... :lol:

Oops we did.

JR

PS: BTW I found a partial tube of old panasonic MN3001 BBD chips.... I doubt these are in high demand these days but $15-$20 ea back in the 70s
"And we still do both old and new."
(And it rhymes. :lol:)

I think the MN3001 are in demand.
We used the MN3001 in the "Time Warp" at MicMix.

Re: Low Noise Transistors: Comparing the ZTX1053A and ZDT1053 (Dual) vs. the ZTX689B and ZTX851

Posted: Tue Mar 17, 2020 9:51 pm
by JR.
mediatechnology wrote:
Tue Mar 17, 2020 4:44 pm
JR. wrote:
Tue Mar 17, 2020 4:00 pm
If only we had these devices back in the day.... :lol:

Oops we did.

JR

PS: BTW I found a partial tube of old panasonic MN3001 BBD chips.... I doubt these are in high demand these days but $15-$20 ea back in the 70s
"And we still do both old and new."
(And it rhymes. :lol:)

I think the MN3001 are in demand.
We used the MN3001 in the "Time Warp" at MicMix.
I recall the Panasonic distributor (in NJ) threatening to cut me off because I was selling them for less than full retail through my kit business... I told them sorry but 500,000 copies of that kit article are already out in the world. They demurred. 8-)

JR

Re: Low Noise Transistors: Comparing the ZTX618 and ZTX1049A to the ZTX851

Posted: Thu Mar 19, 2020 3:53 pm
by mediatechnology
Image
Low noise transistors. Comparing the ZTX618 (top), ZTX1049 (top, overlaid) to the ZTX851 (bottom).

Comparing the ZTX851 to the ZTX618 and ZTX1049A.

ZTX851 433pV√Hz
ZTX618 622pV√Hz
ZTX1049A 638pV√Hz

I decided to look at the ZTX618 and ZTX1049A because they were low VceSat transistors and had high hFE. (Both are around 400 typical.)
Low VceSat, in the Zetex line, tends to correlate with low noise, low rbb' characteristics.

Both the ZTX618 and ZTX1049 are a tad noisier than the superb ZTX851 but good enough when higher current gain is required.
For mic impedances all of the ZTX transistors I've tested are more than adequate being << 1nV√Hz.

Re: Low Noise Transistors: Comparing the ZTX951, 2SB737 and ZTX789A

Posted: Fri Mar 20, 2020 2:25 pm
by mediatechnology
A noise comparison of the ZTX951, 2SB737 and ZTX789A.

Image
Low noise transistors. Comparing the ZTX789A (top), 2SB737 (middle) to the ZTX951 (bottom).

Noise density:

ZTX951 376pV√Hz
2SB737 496pV√Hz
ZTX789A 673pV√Hz

Re: Low Noise Transistors: Comparing the ZTX1053A and ZDT1053 (Dual) vs. the ZTX689B and ZTX851

Posted: Tue Apr 07, 2020 3:51 pm
by terkio
mediatechnology wrote:
Tue Mar 10, 2020 3:15 pm
The ZTX1053 looks ideal for mic preamps.
hFE for the ZTX1053 I tested ranged from 300-500 at low test currents.
Cobo is also low-ish around 21 pF.

With the ZTX1053 single looking so promising I'll be checking the dual ZDT1053.
I bought 6 - the Vos spread of the pairs was <<500 µV on all 6.
Great for mic preamps.
What is the hFE spread ?
You measured 300 - 500 about singles.
What matching accuracy can we expect from a batch of ZTX1053 ? Depending of batch size.
What about the hFE spread of the dual ZDT1053.
Should we go with duals or go with singles that we have carefully matched ?

Re: Low Noise Transistors: Comparing the ZTX1053A and ZDT1053 (Dual) vs. the ZTX689B and ZTX851

Posted: Tue Apr 07, 2020 5:15 pm
by mediatechnology
I haven't tested enough of the alternative higher-hFE transistors to know but my experience with the ZTX851 shows that devices which have a good Vbe match usually have close hFE.

As best as I can recall the hFE difference is usually <=5% often better with the ZTX851 when the Vos is matched <500 uV.
Occasionally I find a pair that has a close Vbe match and a large hFE mis-match but they're odd-balls.

Re: Low Noise Transistors: Comparing the ZTX1053A and ZDT1053 (Dual) vs. the ZTX689B and ZTX851

Posted: Tue Apr 07, 2020 8:04 pm
by terkio
I am thinking about matching for a Vbe / Hfe compromise.

Considering a preamp with two 1K bias resistors.
Hfe 400, 5% Hfe match, 4 mA Ic.

We have Ib 10uA.
5% gives delta Ib 500nA
So, we have delta Vb 500uV, which is consistent with delta Vbe 500uV.
In the preamp, we want delta Ve < 500uV

What I have in mind is using a matching gig where I insert a resistor in the transitor base to represent the bias resistor that will be used in the final circuit.