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: <https://imgur.com/a/NZM9lBl> While preserving the low-frequency response
Lambda diode gyrator, pt 2
Started by ●July 9, 2019
Reply by ●July 9, 20192019-07-09
On Tue, 9 Jul 2019 12:02:02 -0400, bitrex <user@example.net> wrote:>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: > ><https://imgur.com/a/NZM9lBl> > >While preserving the low-frequency responseWhy not a capacitor and a resistor as a highpass? That will go to GHz. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●July 9, 20192019-07-09
On 7/9/19 12:04 PM, John Larkin wrote:> On Tue, 9 Jul 2019 12:02:02 -0400, bitrex <user@example.net> wrote: > >> 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: >> >> <https://imgur.com/a/NZM9lBl> >> >> 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
Reply by ●July 9, 20192019-07-09
On Tue, 9 Jul 2019 14:14:06 -0400, bitrex <user@example.net> wrote:>On 7/9/19 12:04 PM, John Larkin wrote: >> On Tue, 9 Jul 2019 12:02:02 -0400, bitrex <user@example.net> wrote: >> >>> 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: >>> >>> <https://imgur.com/a/NZM9lBl> >>> >>> 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 oneI 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. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●July 9, 20192019-07-09
On 7/9/19 2:18 PM, John Larkin wrote:> On Tue, 9 Jul 2019 14:14:06 -0400, bitrex <user@example.net> wrote: > >> On 7/9/19 12:04 PM, John Larkin wrote: >>> On Tue, 9 Jul 2019 12:02:02 -0400, bitrex <user@example.net> wrote: >>> >>>> 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: >>>> >>>> <https://imgur.com/a/NZM9lBl> >>>> >>>> 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.
Reply by ●July 9, 20192019-07-09
On 7/9/19 2:30 PM, bitrex wrote:> On 7/9/19 2:18 PM, John Larkin wrote: >> On Tue, 9 Jul 2019 14:14:06 -0400, bitrex <user@example.net> wrote: >> >>> On 7/9/19 12:04 PM, John Larkin wrote: >>>> On Tue, 9 Jul 2019 12:02:02 -0400, bitrex <user@example.net> wrote: >>>> >>>>> 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: >>>>> >>>>> <https://imgur.com/a/NZM9lBl> >>>>> >>>>> 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
Reply by ●July 9, 20192019-07-09
On 7/9/19 2:18 PM, John Larkin wrote:> On Tue, 9 Jul 2019 14:14:06 -0400, bitrex <user@example.net> wrote: > >> On 7/9/19 12:04 PM, John Larkin wrote: >>> On Tue, 9 Jul 2019 12:02:02 -0400, bitrex <user@example.net> wrote: >>> >>>> 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: >>>> >>>> <https://imgur.com/a/NZM9lBl> >>>> >>>> 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. > >There used to be a Bob Pease video on YT where he designed a floating inductance gyrator of very large value like 1H or something, someone posted it here at one point, idk if anyone agreed with my belief at the time that a floating 1H equivalent inductance gyrator that's limited to tens of uA of output current is IMO a fucking useless device it's a resistor made with like 12 parts
Reply by ●July 9, 20192019-07-09
On Tuesday, July 9, 2019 at 2:23:15 PM UTC-4, John Larkin wrote:> On Tue, 9 Jul 2019 14:14:06 -0400, bitrex <user@example.net> wrote: > > >On 7/9/19 12:04 PM, John Larkin wrote: > >> On Tue, 9 Jul 2019 12:02:02 -0400, bitrex <user@example.net> wrote: > >> > >>> 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: > >>> > >>> <https://imgur.com/a/NZM9lBl> > >>> > >>> 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 >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.> 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. >> > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
Reply by ●July 9, 20192019-07-09
On 7/9/19 8:27 PM, George Herold wrote:> On Tuesday, July 9, 2019 at 2:23:15 PM UTC-4, John Larkin wrote: >> On Tue, 9 Jul 2019 14:14:06 -0400, bitrex <user@example.net> wrote: >> >>> On 7/9/19 12:04 PM, John Larkin wrote: >>>> On Tue, 9 Jul 2019 12:02:02 -0400, bitrex <user@example.net> wrote: >>>> >>>>> 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: >>>>> >>>>> <https://imgur.com/a/NZM9lBl> >>>>> >>>>> 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 >> > > 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: <https://www.mouser.com/datasheet/2/212/F3294_MMK-1101858.pdf> about $1 in singles, 50 cent in hundreds for the 63VDC type. the loss tangent is rated at <= 0.005 @ 1kHz.
Reply by ●July 10, 20192019-07-10
On 7/9/19 2:18 PM, John Larkin wrote:> On Tue, 9 Jul 2019 14:14:06 -0400, bitrex <user@example.net> wrote: > >> On 7/9/19 12:04 PM, John Larkin wrote: >>> On Tue, 9 Jul 2019 12:02:02 -0400, bitrex <user@example.net> wrote: >>> >>>> 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: >>>> >>>> <https://imgur.com/a/NZM9lBl> >>>> >>>> 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. > >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 -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
