What is the difference between them? At what max frequencies can rectify ac current?

 

hi,
Read these two datasheets, what do you see.?
When you have a technical query on a device, download a d/s.

E

 

So the 1n4148 looks to be faster right? But how u can see their frequency limit that they can rectify?

 

So the 1n4148 looks to be faster right?

The UF4007's reverse recovery time is almost 20 times that of the 1N4148; and it has 4 times the junction capacitance. So yes, the 1N4148 is "faster."

But how u can see their frequency limit that they can rectify?

Because that is not something determined by diode characteristics alone; it depends on the particular circuit in which it is used, the voltages across and current through the diode, and the characteristics of the other components in that circuit.

In other words, "frequency limit that they can rectify" is something you yourself will have to determine, either through circuit analysis or empirically.

 

The diode capacitance, reverse recovery time and current generally determine the upper frequency it can rectify in your circuit.
If this is for high-frequency rectification of power, then Schottky diodes are usually used, since they have essentially no reverse recovery time.

 

I am planning to construct a voltage multiplier circuit using 10nf caps at high frequencies, about 50khz. Which type of diodes do you suggest?

 

You did not say what voltage you are aiming for and how many voltage doubling stages.

 

The reverse breakdown voltage of a 1N4148 is much lower than the UF4007. What is actually required in the circuit will depend on the design.

Do not just jump to the highest voltage rating available for diodes. This is a common recommendation here at AAC and elsewhere. It is generally OK, apart from cost, for slow general purpose diodes used at AC mains frequencies. It is bad advice for fast recovery rectifiers and Schottky diodes. The forward voltage of Schottky diodes will be higher for higher voltage rating in the same type number group. The reverse recovery time of fast and ultrafast rectifiers will be longer for higher voltage parts in the same type number group. The UF4005 and above are substantially slower than those up to UF4004.

EDIT - While Schottky diodes are very fast, there are few choices available with reverse breakdown greater than 100 V in silicon types. There are high voltage silicon carbide Schottky rectifiers available, but they are fairly expensive and have quite high forward voltage (which often is not very important where they are otherwise well suited).

 

You did not say what voltage you are aiming for and how many voltage doubling stages.

About 330v AC full wave with x6 stage for each cycle for total of 12 stages to generate about 4kv

 

About 330v AC full wave

If you want to rectify that high a voltage, why were you asking about a low-voltage 1N4148 diode.

What is the frequency of this voltage?

 

The max voltage on each diode and capacitor would be only 330v

https://upload.wikimedia.org/wikipe...ade.svg/640px-Stacked_Villard_cascade.svg.png

I just want them to use on the above circuit, i will make one inverter that it will produce about 330v AC at about 50khz

 

So has anybody any idea on what diodes can be used for the above circuit at about 50khz ac frequency?

 

So has anybody any idea on what diodes can be used for the above circuit at about 50khz ac frequency?

Diodes intended for switching mode power supplies would be a good choice because they are intended for high frequency higher current applications. For those, check the Texas Instruments (TI) website. A 1N41418 diode is a signal diode and not suitable for most power applications. And a 1N4007 is a 1 amp 600volt power diode for ac line powered supplies. A quite good part for 60Hz applications.

 

The UF400x series is quite a good choice for what you require. They are fast enough to keep the reverse recovery loss quite low, easy to get and inexpensive. I've used them in switch mode power supplies at over 100 kHz. You might find something a little better from Diodes Incorporated, Vishay or ON Semiconductor, but I doubt if you'll find anything much better that isn't quite a lot more expensive. There are very few really fast diodes similar to the 1N4148 rated at more than 200 PIV. Silicon carbide Schottky diodes are really fast but also expensive.

EDIT: Last time I ordered words, I accidentally ordered twice my usual quantity of "quite" which was quite silly because they take quite a lot of space to store so I'm quite anxious to use some of them up quite quickly.
I think that's quite sufficient Saturday silliness for now.

 

The UF400x series is quite a good choice for what you require. They are fast enough to keep the reverse recovery loss quite low, easy to get and inexpensive. I've used them in switch mode power supplies at over 100 kHz. You might find something a little better from Diodes Incorporated, Vishay or ON Semiconductor, but I doubt if you'll find anything much better that isn't quite a lot more expensive. There are very few really fast diodes similar to the 1N4148 rated at more than 200 PIV. Silicon carbide Schottky diodes are really fast but also expensive.

EDIT: Last time I ordered words, I accidentally ordered twice my usual quantity of "quite" which was quite silly because they take quite a lot of space to store so I'm quite anxious to use some of them up quite quickly.
I think that's quite sufficient Saturday silliness for now.

Say WHAT???