New version and (Re: Haible_Juergen's comments on VCO)

Joachim Verghese jocke at netcontrol.fi
Mon Jun 12 16:08:04 CEST 1995


On Mon, 12 Jun 1995, Rick Jansen wrote:

> I thought so, but the data sheet is a bit confusing. The HC(T)4066 
> can switch voltages up to 12V, but it may be that this means voltages
> between -6V and +6V. In the latest version the cap voltage is 
> less than 5 V, with control signals of 5V.

The VCC of the 74HC4066 can be as high as +12V, right, but remember
that the voltage on the device's pins must be within the range
GND...VCC. In other words, if you supply +5V to the HC4066's VCC
pin, all signal pins must be within 0...5V at all times.

Another thing: in order to achieve the lowest possible on-resistance,
you have to drive the control pins as close to VCC as possible.
Similarly, for the highest possible off-resistance, the control pins
should be driven close to GND. A CMOS device (74HC74) will do this,
but not a TTL (7474, 74LS74).

BTW, for one of my VCO designs I use a CD4066 at +12V which discharges
8V off a 1 nF cap in approx. 2 us. That's good enough for me. No need
for multiple supply voltages, etc.

If you're still interested in different switches, there's the DG201
which can be supplied with +-15V and controlled by +5V logic. Ron
is around 25...30 ohms, and the signal voltage range extends to the
supplies. There are different versions, high speed, CMOS, JFET, etc,
and there are plenty of second sources. ADG201, HI3-0201, LF13201...

-joachim



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