With a more appropriate op amp and better choice of operating point for the diode it looks like the lambda diode load really does provide a significant bandwidth improvement as compared to a resistive load for the gyrator in the high-pass configuration, about 4x, here:
While preserving the low-frequency response
Why not a capacitor and a resistor as a highpass? That will go to GHz.
The "L"-R highpass is the simplest example I could think of for experimenting with using the LD this way.
I can't of a great real-world use case for a LR gyrator high-pass structure off the top of my head, maybe someone knows of one
I never understood the appeal of gyrators. One opamp, or one LC, makes a second-order section.
Maybe they have some advantages for on-chip analog filters. JT used to like them.
They were probably more attractive at a certain time when cost of op-amp sections had fallen to make them almost-jellybeans but precision components were not and there were advantages wrt component tolerance variation. 0.1% resistors and caps aren't going to break the bank nowadays.
They're useful for simulating very large inductances IIRC there was a JT patent for a FSK modem that used a gyrator as the inductance in a parallel RL to make a narrowband filter for some laughably low frequency by today's standards like 25kHz or something.
parallel LC, rather
Well for me it was that can get good caps, (and inductors, are more complicated.)
I like the state variable filter... and better opamps, make it better. (mostly 100k Hz and below.)
Speaking of caps. Is there a good, (good means mostly low dissipation factor, though size/ price also matters.)
1 uF cap? At 0.1 uF I'm using cog ceramics. Maybe I should just stack up 0.1uF ceramics and add some more R? (I'm using some polystyrene automotive ones from DK in the current design, but DF is not great.)George H.
Which are the ones you're using now, specifically? 1uF polystyrene caps sounds pricey and large!
The PCB mount plastic caps I've used in that range before are these metalized polyester EVOX/KEMET units:
about $1 in singles, 50 cent in hundreds for the 63VDC type. the loss tangent is rated at
The main benefit of op amp gyrators is low component sensitivity--it's
0.5, just like a passive LC. I've never used a built-up one either.On the other hand, a cap multiplier is also a gyrator. ;)
Cheers
Phil Hobbs
I designed the Winch Control Intercommunications Subsystem for the C5A. Part of it was a very c-multiplier-like circuit to filter the DC supply for the audio parts. There is a clever RC circuit that has a gain of over 1, and I discovered it by accident; my c-multiplier oscillated.
That makes sense. Raw polystyrene is an almost ideal dielectric except that the Dk is low and can't be made that thin. I have some 0.22uF polystyrene caps and they're really big and probably cost a lot (can't remember what I paid for 'em exactly, though.)
Polypropylene is generally OK. IIRC Win has some stuff on dielectrics in AoE3. Polystyrene caps went away because it melts at 100C, which makes reflow soldering sort of hard unless you're using Wood's metal or something.
Cheers
Phil Hobbs
Yeah we use to buy more polypropylene caps. But now all the lower voltage ones seem to have gone away, so you are stuck with higher voltage (bigger) ones. I use more COG ceramics.. but they top out at ~ 0.1 uF. (just went searching DK again for large value cog ceramics)
George H.
Polyphenylene Sulfide is also good as polyproylene at low volatges but try and get through-hole parts instead of SMD which can deliminate in reflow.
piglet
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