Post on 15-Feb-2019
1WOLTE 96, LEUVEN, BELGIUM, 26-28 JUNE, 1996
CRYOGENIC ASICs IN GaAs FOR APPLICATIONS WITH PARTICLE
DETECTORS
Daniel Victor Camin and Gianluigi Pessina
Dipartimento di Fisica dell’Università and INFN Istituto Nazionale di Fisica Nucleare
Via Celoria 16, 20133 Milano, Italy
A SINGLE-ENDED/
DIFFERENTIAL VOLTAGE
SENSITIVE PREAMPLIFIERFOR
VERY LOW TEMPERATURE DETECTORS
A
BUFFER/SHAPER
LED DRIVER
FOR
LIQUID ARGON
CALORIMETER
MOTIVATIONS
Many applications with cryogenic particle detectors require touse a front-end electronic capable to work close to the detector, to minimise parasitic effects.
We present two examples of monolithic preamplifiers designedand realised for two different detectors:
2WOLTE 96, LEUVEN, BELGIUM, 26-28 JUNE, 1996
HOW A THERMAL DETECTOR OPERATES:
EXAMPLE: A BOLOMETRIC DETECTOR
CHARACTERISTICS: IF THE ABSORBING CRYSTAL HAS A LARGE MASS THE THERMALCONDUCTANCES KT AND KG LIMIT THE SIGNAL BANDWIDTH TO A FEW TENS OFHz.
IF THE BOLOMETER IS SMALL ITSSIGNAL BANDWIDTH IS LIMITED TO A FEW kHz BY THE SPEED OF SOUND AND THE THERMAL CONDUCTANCE Ke.
CT
K
K K
G
T B
C e
+
_
Δv
KEL
ΙIMPINGINGPARTICLE
CB
ΔT = ECT
Abso
rbin
gC
ryst
al
Ke
ThermistorLattice Electron Gas
wThe absorbing crystal heats up of an amount E/CT.
wThe temperature relaxation after the absorbed energy is throw KTand KG.
wThe temperature flow throw KG heats up the Thermistor lattice.
wThe flow throw Ke, inside the Thermistor, in turn heats up the electron gas temperature.
wA modification of the electron gas resistance occurs.
wA change in the voltage across the biased resistance is measuredproportional to the initial temperature increase.
BASE TEMPERATURE 10÷100mK
3WOLTE 96, LEUVEN, BELGIUM, 26-28 JUNE, 1996
WHY A SINGLE-ENDED/DIFFERENTIAL MONOLITHICPREAMPLIFIER FOR 4.2K TEMPERATURE
A VERY IMPORTANT SOURCE OF NOISE: VIBRATIONS OF THEELECTRICAL LINK
cP
AB
SO
RB
ING
CR
YS
TAL
TEMPERATURESENSOR
MECHANICALVIBRATIONS OFWIRES
THE FREQUENCY SPECTRUM OF THIS NOISE SOURCESIS WELL INSIDE THE SIGNAL BANDWIDTH OF THESE DETECTORS.
The fluctuations of the wire change the parasitic capacitance CP ofthe link, inducing a charge signal on the temperature sensor, which increases the temperature and develops an unwantedsignal voltage.
SINGLE-ENDED PREAM.:USEFUL WHEN THE SENSOR HAS A LOW IMPEDANCE (Tunnel Junction, TransitionThermometers, etc..): charge injection hasminimal effect.
cP
AB
SO
RB
ING
CR
YS
TAL
TEMPERATURESENSOR
+
-
cP
DIFFERENTIAL PREAM.:USEFUL WHEN THE SENSOR HAS A LARGEIMPEDANCE(Thermistors): chargesinjection generates the same signal at the pream. inputs, which gives no effects on the thermistor. At the output it cancels.
4WOLTE 96, LEUVEN, BELGIUM, 26-28 JUNE, 1996
PREAMPLIFIER CONCEPT
++ __RBRB
RA RA
A
VEE
RG
SINGLE-ENDEDDIFFERENTIAL SWITCH
A B
4 TWO SINGLE ENDED PREAMPLIFIERS ARE SYMMETRICALLY JOINED AT LINE A.
4 EACH PREAMPLIFIER HAS ONLY ONE MESFET AT THE INPUT, SAVING NOISE.
4 IF THE SWITCH IS CLOSED THE TWO PREAMPLIFIER ARE MADE INDEPENDENT: THEY BEHAVE AS A TWO CHANNELPREAMPLIFIER.
4 IF THE SWITCH IS OPEN THE PREAMPLIFIERS BEHAVE ASA DIFFERENTIAL INSTRUMENTATION PREAMPLIFIER AND RESISTOR RG SINK THE STANDING CURRENT.
5WOLTE 96, LEUVEN, BELGIUM, 26-28 JUNE, 1996
SINGLE-ENDED CIRCUIT PREAMPLIFIER CONCEPT
Vcc
IN+
OUT+
RB
OFFSET ADJUST
RA
RB
RA
+ _
VEE
VEE
A
A: The input MESFET Qi is Bootstrapped by Q1
Qi
Q1
Q2
B: Q2 cascodes the input bootstrap.
B
C
C: Active load, a bootstrapped current source
D
D: Common Source stage with active load andbuffer driver.
RC
Q1
Qi
Q2
Q3
Q3
Q4
Q4
6WOLTE 96, LEUVEN, BELGIUM, 26-28 JUNE, 1996
VEE
VDD VDD
IN+ IN-
OUT+ OUT-
RARA
RB RB
OA
S2
S1
D1
RG
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8RCR1
RV
IB
R2
OB
Qi Qi
DIFFERENTIAL CIRCUIT PREAMPLIFIER CONCEPTAND STATIC OPERATING SETTING
DIFFERENTIAL CONFIGURATION:
POSITIVE SUPPLY VOLTAGE: VCC ≥ 3V(BEST FOR NOISE 4V)
NEGATIVE SUPPLY VOLTAGE: VEE ≤ -1.5V(OFFSET DEPENDENT)
POWER DISSIPATION VCC=4V, VEE ≈ -2.5V, PD=37mW
SINGLE-ENDED CONFIGURATION:
POSITIVE SUPPLY VOLTAGE: VCC ≥ 3V(BEST FOR NOISE 3.5V)
A) NEGATIVE SUPPLY VOLTAGE: VEE ≤ -1.5V (S1 TO VEE, S2 TO GND)(OFFSET DEPENDENT)
POWER DISSIPATION, CASE B), VCC=3.5V, VEE ≈ 0.3V, PD=25mW (Total, for both channels)
B) NEGATIVE SUPPLY VOLTAGE: VEE FOR OFFSET COMPENSATION(S1 TO VEE , S2 TO D1)
7WOLTE 96, LEUVEN, BELGIUM, 26-28 JUNE, 1996
LAYOUT AND GEOMETRY
TWO MESFET CAN BE PUT IN PARALLEL,EACH ONE HAVING LxG= 3x6000μm2
THE 2 CHANNELSARE SEPARATEDTO AVOID CROSSTALK.
Hf
Af
0.1
1
10
100
1 10
Lg (μm)
Af(1
0-12 V2 )
0.1
1
10
100
Hf(10
-26 J)
T = 4KID = 50 μAVDS = 100 - 250 mV
WHY WE USE L=3μm?
δα
vG2 I
DSVDS
L2 V
GS 1gm
2=( )
f
INPUT SERIES LOW FREQUENCY NOISE:
gm gm0W
A +B L=
FOR A MESFET (FOR WHICHELECTRIC FIELD SATURATIONIN THE CHANNEL OCCURS):
( )δα
vG2 I
DS0 V
DS 1gm0
2 A+B L 2
L2 V
GSW
=( )
fTHEN:
EXPERIMENTS:
2mm
2.5mm
(AT LEAST WITHSMALL LG)
8WOLTE 96, LEUVEN, BELGIUM, 26-28 JUNE, 1996
RESULTS AT 4.2K TEMPERATURE
1
10
100
1000
10 100 1000 10000
f (Hz)
nV/√Hz T=4kVcc=4V Vee=-2.6V
-0.7-0.5-0.3-0.10.10.3
0 100 200 300 400
VOUT (mV)
Err. %
606570758085
1 10 100 1000 10000
Hz
dB
1
10
100
1000
10 100 1000 10000
f (Hz)
nV/√Hz T=77kVcc=4V Vee=-2.
DIFFERENTIAL SIGNAL
FREQUENCY BANDWIDTH:ABOUT 3MHz
COMMON MODE REJECTIONRATIO.CROSS-TALK BETWEENCHANNELS IN SINGLE-ENDEDMODE WAS NOT MEASURABLE
75dB
INTEGRAL NON-LINEARITY
LESS THAN 0.3% IN THE 250mVOUTPUT VOLTAGE, CORRESPONDING TO ABOUT30mV OF DIFF. INPUT.THE GAIN IS 11
THE NOISE @ 4.2K HAS A 1/fSLOPE AT LOW FREQUENCY.INPUT MESFET WORKING POINTWAS: VDS≈ 0.4V, IDS=2.5mA.
90nV/√Hz@ 100Hz