What XTAL OSC is this?

[Andrew Holme]

What is this oscillator configuration called?

It seems to have some good and useful features: easy to control XTAL drive
level; operates in series resonant mode; differential square-ish wave output
with fast rise time; very good amplitude stability versus supply voltage
variation; no relaxation mode if crystal removed; no need to tune-out C0
holder capacitance; simple single-point power-supply decoupling.

What are the disadvantages? Two active devices = more noise? But the
Butler and Driscoll circuits use two active devices. No LC frequency
selectivity to force XTAL onto correct harmonic? But that could be added...

TIA

LTSpice .ASC file:

Version 4
SHEET 1 928 744
WIRE -80 -160 -128 -160
WIRE 48 -160 0 -160
WIRE 96 -160 48 -160
WIRE 224 -160 176 -160
WIRE 48 -112 48 -160
WIRE 48 0 48 -32
WIRE -128 48 -128 -160
WIRE -16 48 -128 48
WIRE 224 48 224 -160
WIRE 224 48 112 48
WIRE -128 128 -128 48
WIRE 224 128 224 48
WIRE -16 176 112 48
WIRE -16 176 -64 176
WIRE 112 176 -16 48
WIRE 160 176 112 176
WIRE -128 272 -128 224
WIRE 32 272 -128 272
WIRE 224 272 224 224
WIRE 224 272 96 272
WIRE -128 384 -128 272
WIRE -80 384 -128 384
WIRE 32 384 0 384
WIRE 112 384 96 384
WIRE 224 384 224 272
WIRE 224 384 192 384
WIRE 224 432 224 384
WIRE 352 432 224 432
WIRE -128 480 -128 384
WIRE 224 480 224 432
WIRE 352 480 352 432
WIRE -128 608 -128 560
WIRE 224 608 224 560
WIRE 352 608 352 560
FLAG 48 0 0
FLAG 224 608 0
FLAG 352 608 0
FLAG -128 608 0
SYMBOL voltage 48 -128 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value 5
SYMBOL npn 160 128 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL npn -64 128 M0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL current 352 480 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName I2
SYMATTR Value SINE(0 1e-3 10e6 0 0 0 10)
SYMBOL ind -96 400 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 5 56 VBottom 0
SYMATTR InstName L1
SYMATTR Value 0.0253303
SYMATTR SpiceLine Rpar=1e300
SYMBOL cap 96 368 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C1
SYMATTR Value 10f
SYMBOL res 208 368 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R1
SYMATTR Value 20
SYMBOL res 192 -176 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL res 16 -176 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R3
SYMATTR Value 1k
SYMBOL cap 96 256 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C0
SYMATTR Value 5p
SYMBOL res 208 464 R0
SYMATTR InstName R4
SYMATTR Value 3k3
SYMBOL res -144 464 R0
SYMATTR InstName R5
SYMATTR Value 3k3
TEXT 16 600 Left 0 !.tran 1m

 

[Andrew Holme]

What is this oscillator configuration called?

It seems to have some good and useful features: easy to control XTAL drive
level; operates in series resonant mode; differential square-ish wave
output with fast rise time; very good amplitude stability versus supply
voltage variation; no relaxation mode if crystal removed; no need to
tune-out C0 holder capacitance; simple single-point power-supply
decoupling.

What are the disadvantages? Two active devices = more noise? But the
Butler and Driscoll circuits use two active devices. No LC frequency
selectivity to force XTAL onto correct harmonic? But that could be
added...

TIA

LTSpice .ASC file:

Version 4
SHEET 1 928 744
WIRE -80 -160 -128 -160
WIRE 48 -160 0 -160
WIRE 96 -160 48 -160
WIRE 224 -160 176 -160
WIRE 48 -112 48 -160
WIRE 48 0 48 -32
WIRE -128 48 -128 -160
WIRE -16 48 -128 48
WIRE 224 48 224 -160
WIRE 224 48 112 48
WIRE -128 128 -128 48
WIRE 224 128 224 48
WIRE -16 176 112 48
WIRE -16 176 -64 176
WIRE 112 176 -16 48
WIRE 160 176 112 176
WIRE -128 272 -128 224
WIRE 32 272 -128 272
WIRE 224 272 224 224
WIRE 224 272 96 272
WIRE -128 384 -128 272
WIRE -80 384 -128 384
WIRE 32 384 0 384
WIRE 112 384 96 384
WIRE 224 384 224 272
WIRE 224 384 192 384
WIRE 224 432 224 384
WIRE 352 432 224 432
WIRE -128 480 -128 384
WIRE 224 480 224 432
WIRE 352 480 352 432
WIRE -128 608 -128 560
WIRE 224 608 224 560
WIRE 352 608 352 560
FLAG 48 0 0
FLAG 224 608 0
FLAG 352 608 0
FLAG -128 608 0
SYMBOL voltage 48 -128 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value 5
SYMBOL npn 160 128 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL npn -64 128 M0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL current 352 480 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName I2
SYMATTR Value SINE(0 1e-3 10e6 0 0 0 10)
SYMBOL ind -96 400 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 5 56 VBottom 0
SYMATTR InstName L1
SYMATTR Value 0.0253303
SYMATTR SpiceLine Rpar=1e300
SYMBOL cap 96 368 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C1
SYMATTR Value 10f
SYMBOL res 208 368 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R1
SYMATTR Value 20
SYMBOL res 192 -176 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL res 16 -176 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R3
SYMATTR Value 1k
SYMBOL cap 96 256 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C0
SYMATTR Value 5p
SYMBOL res 208 464 R0
SYMATTR InstName R4
SYMATTR Value 3k3
SYMBOL res -144 464 R0
SYMATTR InstName R5
SYMATTR Value 3k3
TEXT 16 600 Left 0 !.tran 1m

I think there is a trade-off between working-Q and drive level. The crystal
is in series with 2*re. The lower re, the higher Qw. Unfortunately,
reducing re means increasing Ie which increases drive. Nevertheless, quite
a reasonable compromise may be possible.

 

[Jamie]

Come on, Phil, were we starting from 'quality' ?

Send some Mexicans to NY ;-)

...Jim Thompson

There are plenty already there!

 

[Andrew Holme]

[big snip]

You're kidding with that bias scheme, right? You really want amplitude
limiting from BJT saturation? Cutoff is much much quieter, but AGC is
where it's at for simple oscillators (e.g. your MC1648 from long ago) and
bridge circuits can pretty well eliminate phase noise due to the active
devices.

What sort of bridge is that Phil? Do you mean like in "A NEW TYPE OF
BALANCED-BRIDGE CONTROLLED OSCILLATOR" by R. K. Karlquist ? Can you provide
any references?

TIA