Confused about IC chips

[Bill_F]

I need to order a CD4069 IC and Farnell offers two. One from Texas Instruments CD4069UBE and one from Fairchild CD4069UBCN.

As I understand it the letters after the UB are the package design. Both of these are 14 lead PDIP's. My question is, are they the same chip with different company designations for the packaging. Then, would it be alright for me to order either one.

If it helps, the pedal is the MXR envelope filter.

Thanks,
Bill

[Peter Snowberg]

You are correct about the suffix codes. Either chip should work fine.

I have an MXR Envelope Filter buried in a box somewhere (I HOPE I still do at least), and I LOVE the sound. It's probably my favorite purchased pedal of all time.

You may want to pick up two of each of those 4069s. Even though they work the same for digital applications, the analog world may bring up subtle differences.

Best of luck on your build!
-Peter

[brett]

When you build your MXR EF, take a look at the build reports at Tonepad.com, they offer some suggestions to help get it wah-ing.  One of the critical bits is the voltage divider that sets the bias  - standard its a 62k and 100k resistor, but that has the 4069 operating on the "shoulder" of its linear operating range (ie with 9V supply, the bias voltage is 100/162x9 = 5.5V).  A better voltage divider is probably 62k/82k or 82k/100k, though I'm certainly no expert on this stuff.

Good luck!

[Bill_F]

Thanks guys.

[gez]

One of the critical bits is the voltage divider that sets the bias  - standard its a 62k and 100k resistor, but that has the 4069 operating on the "shoulder" of its linear operating range (ie with 9V supply, the bias voltage is 100/162x9 = 5.5V).  A better voltage divider is probably 62k/82k or 82k/100k

I haven't used the 4069, but every other inverter chip I've used biases slightly off-centre, suggesting that the trigger from high to low isn't at exactly half the supply.  Maybe this is why an unequal divider was used?

[gez]

PS That part of the circuit looks like a VCO.

[analogguru]

Uxx means unbuffered, thats important in using any c-mos-chip as a FET.

analogguru

[Paul Perry (Frostwave)]

I haven't used the 4069, but every other inverter chip I've used biases slightly off-centre, suggesting that the trigger from high to low isn't at exactly half the supply.  Maybe this is why an unequal divider was used?

Thanks Gez & Brett, this is a subtle point! I think that it is also worth noting that while digital chips aith the same name are interchangable, that doesn't mean that they are the same when used in linear applictions. And really, if linear characteristics aren't specifically defined in the data sheet, even the same manufacturer's chip might vary.