STMICROELECTRONICS TSH350ILT

TSH350
550 MHz, Low Noise Current Feedback Amplifier
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Bandwidth: 550MHz in unity gain
Quiescent current: 4.1mA
Slew rate: 940V/µs
Input noise: 1.5nV/VHz
Distortion: SFDR=-66dBc (10MHz, 1Vp-p)
2.8Vp-p min. output swing on 100Ω load for
a 5V supply
Tested on 5V power supply
Pin Connections (top view)
OUT 1
Description
-VCC 2
The TSH350 is a current feedback operational
amplifier using a very high speed complementary
technology to provide a bandwidth up to 410MHz
while drawing only 4.1mA of quiescent current.
With a slew rate of 940V/µs and an output stage
optimized for driving a standard 100Ω load, this
circuit is highly suitable for applications where
speed and power-saving are the main
requirements.
+-
+IN 3
4 -IN
SOT23-5
8 NC
NC 1
The TSH350 is a single operator available in the
tiny SOT23-5 and SO8 plastic packages, saving
board space as well as providing excellent
thermal and dynamic performances.
-IN 2
_
7 +VCC
+IN 3
+
6 OUT
5 NC
-VCC 4
Applications
■
■
■
5 +VCC
SO8
Communication & Video Test Equipment
Medical Instrumentation
ADC drivers
Order Codes
Part Number
Temperature Range
Package
Conditioning
Marking
TSH350ILT
TSH350ID
TSH350IDT
-40°C
to
+85°C
SOT23-5
SO8
SO8
Tape&Reel
Tube
Tape&Reel
K305
TSH350I
TSH350I
December 2004
Revision 2
1/21
TSH350
Absolute Maximum Ratings
1 Absolute Maximum Ratings
Table 1: Key parameters and their absolute maximum ratings
Symbol
VCC
Vid
Vin
Parameter
Supply Voltage
1
Differential Input Voltage
2
3
Value
Unit
6
V
+/-0.5
V
+/-2.5
V
Toper
Input Voltage Range
Operating Free Air Temperature Range
-40 to + 85
°C
Tstg
Storage Temperature
-65 to +150
°C
150
°C
250
150
°C/W
80
28
°C/W
Maximum Power Dissipation4 (@Ta=25°C) for Tj=150°C
SOT23-5
SO8
500
830
mW
HBM : Human Body Model 5 (pins 1, 4, 5, 6, 7 and 8)
HBM : Human Body Model (pins 2 and 3)
2
kV
0.5
kV
200
V
60
1.5
1.5
200
V
kV
kV
mA
Tj
Rthja
Rthjc
Pmax
ESD
Maximum Junction Temperature
Thermal Resistance Junction to Ambient
SOT23-5
SO8
Thermal Resistance Junction to Ambient
SOT23-5
SO8
MM : Machine Model 6 (pins 1, 4, 5, 6, 7 and 8)
MM : Machine Model (pins 2 and 3)
CDM : Charged Device Model (pins 1, 4, 5, 6, 7 and 8)
CDM : Charged Device Model (pins 2 and 3)
Latch-up Immunity
1) All voltages values are measured with respect to the ground pin.
2) Differential voltage are non-inverting input terminal with respect to the inverting input terminal.
3) The magnitude of input and output voltage must never exceed VCC +0.3V.
4) Short-circuits can cause excessive heating. Destructive dissipation can result from short circuit on amplifiers.
5) Human body model, 100pF discharged through a 1.5kΩ resistor into pMin of device.
6) This is a minimum Value. Machine model ESD, a 200pF cap is charged to the specified voltage, then discharged directly into the IC with
no external series resistor (internal resistor < 5Ω), into pin to pin of device.
Table 2: Operating conditions
Symbol
VCC
Vicm
Parameter
1
Supply Voltage
Common Mode Input Voltage
1) Tested in full production at 5V (±2.5V) supply voltage.
2/21
Value
Unit
4.5 to 5.5
V
-Vcc+1.5V to +Vcc-1.5V
V
Electrical Characteristics
TSH350
2 Electrical Characteristics
Table 3: Electrical characteristics for VCC = ±2.5Volts, Tamb = 25°C (unless otherwise specified)
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
0.8
4
Unit
DC performance
Vio
Input Offset Voltage
Offset Voltage between both inputs
Tamb
Tmin. < Tamb < Tmax.
1
∆Vio
Vio drift vs. Temperature
Tmin. < Tamb < Tmax.
0.9
Iib+
Non Inverting Input Bias Current
Tamb
DC current necessary to bias the input +
Tmin. < Tamb < Tmax.
12
Iib-
Inverting Input Bias Current
Tamb
DC current necessary to bias the input Tmin. < Tamb < Tmax.
1
CMR
SVR
PSR
ICC
20 log (∆Vic/∆Vio )
Tmin. < Tamb < Tmax.
Supply Voltage Rejection Ratio
∆Vcc=+3.5V to +5V
20 log (∆Vcc/∆Vio)
Tmin. < Tamb < Tmax.
78
Power Supply Rejection Ratio
AV = +1, ∆Vcc=±100mV
at 1kHz
51
Tmin. < Tamb < Tmax.
48
Positive Supply Current
DC consumption with no input signal
35
20
2.5
∆Vic = ±1V
20 log (∆Vcc/∆Vout)
µV/°C
13
Common Mode Rejection Ratio
56
60
No load
81
4.1
µA
µA
dB
58
68
mV
dB
dB
4.9
mA
Dynamic performance and output characteristics
ROL
Bw
SR
VOH
VOL
Transimpedance
Output Voltage/Input Current Gain in
open loop of a CFA.
For a VFA, the analog of this feature is
the Open Loop Gain (AVD)
∆Vout = ±1V, RL = 100Ω
-3dB Bandwidth
Frequency where the gain is 3dB below
the DC gain AV
Note: Gain Bandwidth Product criterion is
not applicable for Current-FeedbackAmplifiers
Small Signal Vout=20mVp-p
AV = +1, RL = 100Ω
AV = +2, RL = 100Ω
AV = +10, RL = 100Ω
AV = -2, RL = 100Ω
170
270
kΩ
250
kΩ
550
390
125
370
MHz
Tmin. < Tamb < Tmax.
250
Gain Flatness @ 0.1dB
Small Signal Vout=100mVp
Band of frequency where the gain varia- AV = +1, RL = 100Ω
tion does not exceed 0.1dB
65
Slew Rate
Maximum output speed of sweep in
large signal
Vout = 2Vp-p, AV = +2,
RL = 100Ω
940
V/µs
High Level Output Voltage
RL = 100Ω
1.56
V
Low Level Output Voltage
1.44
Tmin. < Tamb < Tmax.
1.49
RL = 100Ω
-1.53
Tmin. < Tamb < Tmax.
-1.49
-1.44
V
3/21
TSH350
Electrical Characteristics
Table 3: Electrical characteristics for VCC = ±2.5Volts, Tamb = 25°C (unless otherwise specified)
Symbol
Iout
Parameter
Test Condition
Isink
Short-circuit Output current coming in
the op-amp.
See fig-8 for more details
Output to GND
Isource
Output current coming out from the opamp.
See fig-11 for more details
Output to GND
Min.
Typ.
135
205
Tmin. < Tamb < Tmax.
Max.
Unit
195
-140
Tmin. < Tamb < Tmax.
mA
-210
-185
Noise and distortion
eN
iN
SFDR
Equivalent Input Noise Voltage
see application note on page 13
F = 100kHz
Equivalent Input Noise Current (+)
see application note on page 13
F = 100kHz
Equivalent Input Noise Current (-)
see application note on page 13
F = 100kHz
Spurious Free Dynamic Range
The highest harmonic of the output
spectrum when injecting a filtered sine
wave
AV = +1, Vout = 1Vp-p
F = 10MHz
F = 20MHz
F = 50MHz
F = 100MHz
1.5
nV/√Hz
20
pA/√Hz
13
pA/√Hz
-66
-57
-46
-42
dBc
Table 4: Closed-loop gain and feedback components
VCC (V)
±2.5
4/21
Gain
Rfb (Ω)
-3dB Bw (MHz)
0.1dB Bw (MHz)
+10
300
125
22
-10
300
120
20
+2
300
390
110
-2
300
370
70
+1
820
550
65
-1
300
350
120
Electrical Characteristics
TSH350
Figure 1: Frequency response, positive gain
24
22
20
12
10
8
Gain=+4
Gain=-4
Gain=+2
12
10
8
Gain=-2
6
4
2
0
-2
6
4
2
0
-2
Gain=+1
-4
-6
-8
Small Signal
Vcc=5V
Load=100Ω
-10
1M
Gain=-10
18
16
14
Gain (dB)
Gain (dB)
24
22
20
Gain=+10
18
16
14
-4
-6
-8
Figure 4: Frequency response, negative gain
10M
100M
Gain=-1
Small Signal
Vcc=5V
Load=100Ω
-10
1M
1G
10M
Figure 2: Compensation, gain=+4
1G
Figure 5: Compensation, gain=+2
12,1
6,2
6,1
Gain Flatness (dB)
12,0
Gain Flatness (dB)
100M
Frequency (Hz)
Frequency (Hz)
11,9
Vin
Vout
+
11,8
-
4pF
300R
100R
6,0
5,9
Vin
Vout
+
-
5,8
8k2
2pF
300R
100R
11,7
5,7
Gain=+4, Vcc=5V,
Small Signal
Gain=+2, Vcc=5V,
Small Signal
11,6
1M
10M
5,6
1M
100M
Frequency (Hz)
10M
100M
1G
Frequency (Hz)
Figure 3: Frequency response vs. capa-load
Figure 6: Step response vs. capa-load
3
10
C-Load=1pF
R-iso=22ohms
C-Load=1pF
R-iso=22ohms
8
2
Output step (Volt)
6
Gain (dB)
4
C-Load=10pF
R-iso=39ohms
2
0
-2
Vin
+
-
C-Load=22pF
R-iso=27ohms
Vout
R-iso
-8
-10
1M
C-Load=22pF
R-iso=27ohms
1
Vin
+
-
300R
300R
0
-4
-6
C-Load=10pF
R-iso=39ohms
300R
300R
1k
Vout
R-iso
1k
C-Load
C-Load
Gain=+2, Vcc=5V,
Small Signal
Gain=+2, Vcc=5V,
Small Signal
-1
0,0s
10M
100M
1G
2,0ns 4,0ns 6,0ns 8,0ns 10,0ns 12,0ns 14,0ns 16,0ns 18,0ns 20,0ns
Time (ns)
Frequency (Hz)
5/21
TSH350
Electrical Characteristics
Figure 7: Slew rate
Figure 10: Output amplitude vs. load
4,0
1,5
1,0
0,5
Gain=+2
Vcc=5V
Load=100Ω
0,0
-2ns
-1ns
0s
1ns
2ns
Max. Output Amplitude (Vp-p)
Output Response (V)
2,0
3,5
3,0
2,5
Gain=+2
Vcc=5V
Load=100Ω
2,0
10
3ns
100
1k
10k
100k
Load (ohms)
Time (ns)
Figure 8: Isink
Figure 11: Isource
300
0
+2.5V
VOL
without load
+
-50
-1V
Isink
_
Isink (mA)
200
V
- 2.5V
RG
Isource (mA)
250
Amplifier in open
loop without load
150
100
-100
-150
+2.5V
VOH
without load
+
+1V
-200
Isource
_
V
- 2.5V
50
0
-2,0
RG
-250
-1,5
-1,0
-0,5
-300
0,0
0,0
0,5
V (V)
2,0
Figure 12: Input voltage noise vs. frequency
70
4.0
60
3.5
Pos. Current
Noise
3.0
en (nV/VHz)
50
in (pA/VHz)
1,5
V (V)
Figure 9: Input current noise vs. frequency
Neg. Current
Noise
40
30
20
2.5
2.0
1.5
10
1k
10k
100k
Frequency (Hz)
6/21
1,0
Amplifier in open
loop without load
1M
10M
1.0
1k
10k
100k
Frequency (Hz)
1M
10M
Electrical Characteristics
TSH350
Figure 13: Quiescent current vs. Vcc
Figure 16: Distortion vs. output amplitude
5
0
-5
4
Icc(+)
-10
-15
3
-20
HD2 & HD3 (dBc)
Icc (mA)
2
1
Gain=+2
Vcc=5V
Input to ground, no load
0
-1
-2
-25
-30
HD2
-35
-40
-45
-50
-55
-60
-3
-4
-70
Icc(-)
-5
1,25
Gain=+2
Vcc=5V
F=30MHz
Load=100Ω
HD3
-65
-75
-80
1,50
1,75
2,00
2,25
0
2,50
1
+/-Vcc (V)
2
3
4
Output Amplitude (Vp-p)
Figure 14: Distortion vs. output amplitude
Figure 17: Noise figure
-20
40
-25
-30
35
-35
30
-45
-50
25
HD2
-55
NF (dB)
HD2 & HD3 (dBc)
-40
-60
-65
-70
20
15
-75
HD3
-80
Gain=+2
Vcc=5V
F=10MHz
Load=100Ω
-85
-90
-95
10
5
-100
Gain=?
Vcc=5V
0
0
1
2
3
4
1
10
100
Output Amplitude (Vp-p)
1k
10k
100k
Rsource (ohms)
Figure 15: Distortion vs. output amplitude
Figure 18: Output amplitude vs. frequency
5
-20
-25
-30
4
-35
Vout max. (Vp-p)
HD2 & HD3 (dBc)
-40
HD2
-45
-50
-55
-60
-65
HD3
-70
-75
-80
Gain=+2
Vcc=5V
F=20MHz
Load=100Ω
-85
-90
-95
1
2
Output Amplitude (Vp-p)
3
2
1
Gain=+2
Vcc=5V
Load=100Ω
-100
0
3
4
0
1M
10M
100M
1G
Frequency (Hz)
7/21
TSH350
Electrical Characteristics
Figure 19: Reverse isolation vs. frequency
Figure 22: SVR vs. temperature
90
0
85
80
SVR (dB)
Isolation (dB)
-20
-40
-60
75
70
65
60
-80
Small Signal
Vcc=5V
Load=100Ω
-100
1M
55
Gain=+1
Vcc=5V
Load=100Ω
50
10M
100M
-40
1G
-20
0
20
40
60
80
100
120
80
100
120
Temperature (°C)
Frequency (Hz)
Figure 20: Bandwidth vs. temperature
Figure 23: ROL vs. temperature
550
340
500
320
450
ROL (MΩ)
Bw (MHz)
300
400
350
300
280
260
240
Gain=+1
250
Vcc=5V
Load=100 Ω
220
Open Loop
Vcc=5V
200
200
-40
-20
0
20
40
60
80
100
-40
120
-20
0
20
40
60
Temperature (°C)
Temperature (°C)
Figure 21: CMR vs. temperature
Figure 24: I-bias vs. temperature
70
14
68
12
66
Ib(+)
10
64
IBIAS (µA)
CMR (dB)
8
62
60
58
6
4
Ib(-)
2
56
0
54
52
Gain=+1
Vcc=5V
Load=100Ω
-2
-4
Gain=+1
Vcc=5V
Load=100Ω
50
-40
-20
0
20
40
60
Temperature (°C)
8/21
80
100
120
-40
-20
0
20
40
60
Temperature (°C)
80
100
120
Electrical Characteristics
TSH350
Figure 25: Vio vs. temperature
Figure 27: Icc vs. temperature
6
1000
4
Icc(+)
800
0
600
ICC (mA)
VIO (micro V)
2
400
-2
Icc(-)
-4
-6
200
Open Loop
Vcc=5V
Load=100Ω
-8
-10
0
-40
-20
Gain=+1
Vcc=5V
no Load
In+/In- to GND
0
20
40
60
80
100
-40
120
-20
0
20
40
60
80
100
120
80
100
120
Temperature (°C)
Temperature (°C)
Figure 26: VOH & VOL vs. temperature
Figure 28: Iout vs. temperature
300
2
200
VOH
1
Isource
100
-1
Iout (mA)
VOH & OL (V)
0
VOL
-2
0
-100
Isink
-200
-3
-4
-300
Gain=+1
Vcc=5V
Load=100Ω
-5
-40
-20
-400
0
20
40
Temperature (°C)
60
80
Output: short-circuit
Gain=+1
Vcc=5V
-40
-20
0
20
40
60
Temperature (°C)
9/21
TSH350
Evaluation Boards
3 Evaluation Boards
An evaluation board kit optimized for high speed operational amplifiers is available (order code:
KITHSEVAL/STDL). The kit includes the following evaluation boards, as well as a CD-ROM containing
datasheets, articles, application notes and a user manual:
l SOT23_SINGLE_HF BOARD: Board for the evaluation of a single high-speed op-amp in SOT23-5
package.
l SO8_SINGLE_HF: Board for the evaluation of a single high-speed op-amp in SO8 package.
l SO8_DUAL_HF: Board for the evaluation of a dual high-speed op-amp in SO8 package.
l SO8_S_MULTI: Board for the evaluation of a single high-speed op-amp in SO8 package in inverting
and non-inverting configuration, dual and signle supply.
l SO14_TRIPLE: Board for the evaluation of a triple high-speed op-amp in SO14 package with video
application considerations.
Board material:
l 2 layers
ε
l FR4 ( r=4.6)
l epoxy 1.6mm
l copper thickness: 35µm
Figure 29: Evaluation kit for high speed op-amps
10/21
Power Supply Considerations
TSH350
4 Power Supply Considerations
Correct power supply bypassing is very important for optimizing performance in high-frequency ranges.
Bypass capacitors should be placed as close as possible to the IC pins to improve high-frequency
bypassing. A capacitor greater than 1µF is necessary to minimize the distortion. For better quality
bypassing, a capacitor of 10nF can be added using the same implementation conditions. Bypass
capacitors must be incorporated for both the negative and the positive supply.
Note:
On the SO8_SINGLE_HF board, these capacitors are C6, C7, C8, C9.
Figure 30: Circuit for power supply bypassing
+VCC
10microF
+
10nF
+
-
10nF
10microF
+
-VCC
Single power supply
In the event that a single supply system is used, new biasing is necessary to assume a positive output
dynamic range between 0V and +VCC supply rails. Considering the values of VOH and V OL, the amplifier
will provide an output dynamic from +0.9V to +4.1V on 100Ω load.
The amplifier must be biased with a mid-supply (nominally +VCC/2), in order to maintain the DC
component of the signal at this value. Several options are possible to provide this bias supply, such as a
virtual ground using an operational amplifier or a two-resistance divider (which is the cheapest solution).
A high resistance value is required to limit the current consumption. On the other hand, the current must
be high enough to bias the non-inverting input of the amplifier. If we consider this bias current (35µA
max.) as the 1% of the current through the resistance divider to keep a stable mid-supply, two resistances
of 750Ω can be used.
The input provides a high pass filter with a break frequency below 10Hz which is necessary to remove the
original 0 volt DC component of the input signal, and to fix it at +VCC/2.
Figure 31 illustrates a 5V single power supply configuration for the SO8_S_MULTI evaluation board (see
Evaluation Boards on page 10).
11/21
TSH350
Power Supply Considerations
A capacitor CG is added in the gain network to ensure a unity gain in low frequency to keep the right DC
component at the ouput. CG contirbutes to a high pass filter with Rfb//RG and its value is calculated with a
consideration of the cut off frequency of this low pass filter.
Figure 31: Circuit for +5V single supply (using evaluation board SO8_S_MULTI)
+5V
10µF
+
IN
+5V
Rin
1kΩ
100µF
_
100Ω
R1
750Ω
Rfb
R2
750Ω
12/21
+ 1µF
RG
10nF
+
CG
OUT
Noise Measurements
TSH350
5 Noise Measurements
The noise model is shown in Figure 32, where:
l eN: input voltage noise of the amplifier
l iNn: negative input current noise of the amplifier
l iNp: positive input current noise of the amplifier
Figure 32: Noise model
+
iN+
R3
output
HP3577
Input noise:
8nV/√Hz
_
N3
eN
iN-
R2
N2
R1
N1
The thermal noise of a resistance R is:
4kTR ∆ F
where ∆F is the specified bandwidth.
On a 1Hz bandwidth the thermal noise is reduced to
4kTR
where k is the Boltzmann's constant, equal to 1,374.10-23J/°K. T is the temperature (°K).
The output noise eNo is calculated using the Superposition Theorem. However eNo is not the simple sum
of all noise sources, but rather the square root of the sum of the square of each noise source, as shown
in Equation 1:
eNo =
e No
2
2
2
2
2
2
2
V1 + V2 + V3 + V4 + V5 + V6
2
2
2
2
2
2
2 R2 2
R2 2
= e N × g + iNn × R2 + iNp × R3 × g + -------- × 4kTR1 + 4kTR2 + 1 + -------- × 4kTR3
R1
R1
Equation 1
Equation 2
13/21
TSH350
Noise Measurements
The input noise of the instrumentation must be extracted from the measured noise value. The real output
noise value of the driver is:
eNo =
2
2
( Measured ) – ( instrumentation )
Equation 3
The input noise is called the Equivalent Input Noise as it is not directly measured but is evaluated from the
measurement of the output divided by the closed loop gain (eNo/g).
After simplification of the fourth and the fifth term of Equation 2 we obtain:
eNo
2
2
2
2
2
2
2
2
R2 2
= eN × g + iNn × R2 + iNp × R3 × g + g × 4kTR2 + 1 + -------- × 4kTR3
R1
Equation 4
Measurement of the Input Voltage Noise eN
If we assume a short-circuit on the non-inverting input (R3=0), from Equation 4 we can derive:
eNo =
2
2
2
2
eN × g + iNn × R2 + g × 4kTR2
Equation 5
In order to easily extract the value of eN, the resistance R2 will be chosen to be as low as possible. In the
other hand, the gain must be large enough:
R3=0, gain: g=100
Measurement of the Negative Input Current Noise iNn
To measure the negative input current noise iNn, we set R3=0 and use Equation 5. This time the gain
must be lower in order to decrease the thermal noise contribution:
R3=0, gain: g=10
Measurement of the Positive Input Current Noise iNp
To extract iNp from Equation 3, a resistance R3 is connected to the non-inverting input. The value of R3
must be chosen in order to keep its thermal noise contribution as low as possible against the iNp
contribution:
R3=100W, gain: g=10
14/21
Intermodulation Distortion Product
TSH350
6 Intermodulation Distortion Product
The non-ideal output of the amplifier can be described by the following series:
2
n
Vout = C + C V + C V in + … C V in
0
1 in
2
n
due to non-linearity in the input-output amplitude transfer, where the input is Vin=Asinωt, C0 is the DC
component, C1(Vin) is the fundamental and Cn is the amplitude of the harmonics of the output signal Vout.
A one-frequency (one-tone) input signal contributes to harmonic distortion. A two-tone input signal
contributes to harmonic distortion and to the intermodulation product.
The study of the intermodulation and distortion for a two-tone input signal is the first step in characterizing
the driving capability of multi-tone input signals.
In this case:
V
in
= A sin ω t + A sin ω t
1
2
then:
V
out
2
n
= C + C ( A sin ω t + A sin ω t ) + C ( A sin ω t + A sin ω t ) … + C ( A sin ω t + A sin ω t )
0
1
1
2
1
2
1
2
2
n
From this expression, we can extract the distortion terms, and the intermodulation terms form a single
sine wave: second order intermodulation terms IM2 by the frequencies (ω1-ω2) and (ω1+ω2) with an
amplitude of C2A2 and third order intermodulation terms IM3 by the frequencies (2ω1-ω2), (2ω1+ω2), (−
ω1+2ω2) and (ω1+2ω2) with an amplitude of (3/4)C3A3.
The measurement of the intermodulation product of the driver is achieved by using the driver as a mixer
by a summing amplifier configuration (see Figure 33). In this way, the non-linearity problem of an external
mixing device is avoided.
Figure 33: Inverting summing amplifier (using evaluation board SO8_S_MULTI)
Vin1
R1
Vin2
R2
Rfb
_
Vout
+
100Ω
R
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TSH350
The Bias of an Inverting Amplifier
7 The Bias of an Inverting Amplifier
A resistance is necessary to achieve a good input biasing, such as resistance R shown in Figure 33.
The magnitude of this resistance is calculated by assuming the negative and positive input bias current.
The aim is to compensate for the offset bias current, which could affect the input offset voltage and the
output DC component. Assuming Ib-, Ib+, Rin, Rfb and a zero volt output, the resistance R will be:
R in × R fb
R = ---------------------R i n + R fb
Figure 34: Compensation of the input bias current
Rfb
Ib-
Rin
_
Vcc+
Output
+
Vcc-
Ib+
R
16/21
Load
Active Filtering
TSH350
8 Active Filtering
Figure 35: Low-pass active filtering, Sallen-Key
C1
R1
R2
+
IN
OUT
C2
_
100Ω
Rfb
RG
From the resistors Rfb and RG we can directly calculate the gain of the filter in a classical non-inverting
amplification configuration:
A
R
fb
g = 1 + ---------=
V
R
g
We assume the following expression as the response of the system:
Vout j ω
g
T ω = ------------------- = --------------------------------------------j
Vin
2
jω
j ω (j ω )
1 + 2 ζ ------- + -------------ωc
2
ω
c
The cut-off frequency is not gain-dependent and so becomes:
ω
1
c = ------------------------------------R1R2C 1C2
The damping factor is calculated by the following expression:
1
ζ = --- ω c ( C1 R 1 + C1 R 2 + C2 R 1 – C1 R 1 g )
2
The higher the gain, the more sensitive the damping factor is. When the gain is higher than 1, it is
preferable to use some very stable resistor and capacitor values. In the case of R1=R2=R:
R
fb
2 C2 – C ---------1R
g
ζ = -----------------------------------2 C C
1 2
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TSH350
Active Filtering
Due to a limited selection of values of capacitors in comparison with resistors, we can fix C1=C2=C, so
that:
R
fb
2 R2 – R 1 ---------R
g
ζ = -----------------------------------2 R R
1 2
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Package Mechanical Data
TSH350
9 Package Mechanical Data
SOT23-5L MECHANICAL DATA
mm.
mils
DIM.
MIN.
TYP
MAX.
MIN.
TYP.
MAX.
A
0.90
1.45
35.4
57.1
A1
0.00
0.15
0.0
5.9
A2
0.90
1.30
35.4
51.2
b
0.35
0.50
13.7
19.7
C
0.09
0.20
3.5
7.8
D
2.80
3.00
110.2
118.1
E
2.60
3.00
102.3
118.1
E1
1.50
1.75
59.0
68.8
e
0 .95
37.4
e1
1.9
74.8
L
0.35
0.55
13.7
21.6
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TSH350
Package Mechanical Data
SO-8 MECHANICAL DATA
DIM.
mm.
MIN.
TYP
inch
MAX.
MIN.
TYP.
MAX.
A
1.35
1.75
0.053
0.069
A1
0.10
0.25
0.04
0.010
A2
1.10
1.65
0.043
0.065
B
0.33
0.51
0.013
0.020
C
0.19
0.25
0.007
0.010
D
4.80
5.00
0.189
0.197
E
3.80
4.00
0.150
0.157
e
1.27
0.050
H
5.80
6.20
0.228
0.244
h
0.25
0.50
0.010
0.020
L
0.40
1.27
0.016
0.050
k
ddd
8˚ (max.)
0.1
0.04
0016023/C
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TSH350
Revision History
10 Revision History
Date
Revision
Description of Changes
01 Oct 2004
1
First release corresponding to Preliminary Data version of datasheet.
December 2004
2
Release of mature product datasheet.
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the
consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from
its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications
mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information
previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or
systems without express written approval of STMicroelectronics.
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