1sv149 or other 20 to >500pF single or dual diode SMD equivalent?

[neazoi]

Hi I am looking for an SMD package equivalent for the 1sv149 or any other 20 to >500pF single or dual diode (like BB212)?
Does it exist?
An LTspice model for it would also be helpful to try it in my design.
Thank you.

 

[FvM]

NXP BB201 is the next best available SMD type.

 

[neazoi]

NXP BB201 is the next best available SMD type.

Thanks a lot,
It goes a max of 120pF though, it is not enough like the 1sv149 or bb212.
I wonder why they don't make these anymore in smd...

 

[betwixt]

Possibly SMD packaging isn't large enough to accommodate the larger surface area of a varicap junction. That's just a guess though.

Some other devices also show large capacitance changes, for example some LEDs, might be worth experimenting. I would anticipate most 'super bright' LEDs having similar characteristics as it is the fluorescent coating that determines their color rather than the junction construction or chemistry.

I've never tried it but possibly the gate-source capcitance of a power MOSFET would work, I'm thinking that they generally have high capacitance to start with but I'm not sure how much it changes with applied reverse voltage.

Brian.

 

[FvM]

Using multiple BB201 in parallel is probably your best option.

Using MOSFETs as varactors is a nice idea, but I guess, the capacitance is considerably lossy. See e.g. Si2343 output capacitance Coss. Vgs has to be shorted.

 

[neazoi]

Using multiple BB201 in parallel is probably your best option.

It is not good because paralleling diodes increases their minimum capacitance

 

[FvM]

It is not good because paralleling diodes increases their minimum capacitance

Paralleling keeps the capacitance ratio, minimum capactance is just proportional to maximum capacitance. The actual problem is that 1SV149 or BB212 have much higher capacitance ratio than BB201.