RHF310
Rad-hard 400 µA high-speed operational amplifier
Preliminary data
Features
■ OptimWatt
consumption and low 400 μA quiescent
current
Bandwidth: 120 MHz (gain = 2)
■
■ Slew rate: 115 V/μs
■ Specified on 1 kΩ
■ Input noise: 7.5 nV/√ Hz
■ Tested with 5 V power supply
■ 300 krad MIL-STD-883 1019.7 ELDRS free
compliant
■ SEL immune at 125° C, LET up to
110 MEV.cm
■ SET characterized, LET up to
110 MEV.cm
■ QMLV qualified under SMD 5962-0723301
■ Mass: 0.45 g
TM
device featuring ultra-low 2 mW
(a)
2
/mg
2
/mg
Applications
■ Low-power, high-speed systems
■ Communication and space equipment
■ Harsh radiation environments
■ ADC drivers
Table 1. Device summary
Pin connections
(top view)
1
NC
IN -
IN +
-VCC
4
The upper metallic lid is not electrically connected to any
pins, nor to the IC die inside the package.
8
NC
+VCC
OUT
NC
5
Description
The RHF310 is a very low power, high-speed
operational amplifier. A bandwidth of 120 MHz is
achieved while drawing only 400 µA of quiescent
current. This low-power characteristic is
particularly suitable for high-speed battery
powered devices requiring dynamic performance.
The RHF310 is a single operator available in a
Flat-8 package, saving board space as well as
providing excellent thermal performance.
Order code SMD pin
RHF310K1 -
Quality
level
Engineering
model
Package
Flat-8 Gold RHF310K1 -
Lead
finish
Marking EPPL Packing
RHF310K-01V 5962F0723301VXC QMLV-Flight Flat-8 Gold 5962F0723101VXC -
Note: Contact your ST sales office for information on the specific conditions for products in die form and
QML-Q versions.
a. OptimWattTM is an STMIcroelectronics registered trademark that applies to products with specific features that optimize
energy efficiency.
July 2011 Doc ID 15577 Rev 3 1/22
This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to
change without notice.
Strip pack
www.st.com
22
Contents RHF310
Contents
1 Absolute maximum ratings and operating conditions . . . . . . . . . . . . . 4
2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3 Power supply considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.1 Single power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4 Noise measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1 Measurement of the input voltage noise eN . . . . . . . . . . . . . . . . . . . . . . . 14
4.2 Measurement of the negative input current noise iNn . . . . . . . . . . . . . . . 14
4.3 Measurement of the positive input current noise iNp . . . . . . . . . . . . . . . . 14
5 Intermodulation distortion product . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6 Bias of an inverting amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7 Active filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.1 Ceramic Flat-8 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2/22 Doc ID 15577 Rev 3
RHF310 List of figures
List of figures
Figure 1. Frequency response, positive gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 2. Frequency response vs. capa-load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 3. Output amplitude vs. load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 4. Input voltage noise vs. frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 5. Distortion at 1 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 6. Distortion at 10 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 7. Positive slew rate on 1 kW load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 8. Negative slew rate on 1 kW load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 9. Quiescent current vs. V
Figure 10. I
Figure 11. I
sink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
source. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 12. Bandwidth vs. temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 13. CMR vs. temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 14. SVR vs. temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 15. Slew rate vs. temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 16. R
Figure 17. I
Figure 18. V
Figure 19. V
Figure 20. I
Figure 21. I
vs. temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
OL
vs. temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
bias
vs. temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
io
and VOL vs. temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
OH
vs. temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
out
vs. temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
CC
Figure 22. Circuit for power supply bypassing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 23. Circuit for +5 V single supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 24. Noise model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 25. Inverting summing amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 26. Compensation of the input bias current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 27. Low-pass active filtering, Sallen-Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Figure 28. Ceramic Flat-8 package mechanical drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
CC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Doc ID 15577 Rev 3 3/22
Absolute maximum ratings and operating conditions RHF310
1 Absolute maximum ratings and operating conditions
Table 2. Absolute maximum ratings
Symbol Parameter Value Unit
V
V
V
T
R
R
P
Supply voltage
CC
(voltage difference between -VCC and +VCC pins)
Differential input voltage
id
Input voltage range
in
Storage temperature -65 to +150 °C
stg
Maximum junction temperature 150 °C
T
j
Thermal resistance junction to ambient area 50 °C/W
thja
Thermal resistance junction to case 40 °C/W
thjc
Maximum power dissipation
max
for T
=150°C
j
HBM: human body model
pins 1, 4, 5, 6, 7 and 8
pins 2 and 3
ESD
MM: machine model
pins 1, 4, 5, 6, 7 and 8
pins 2 and 3
CDM: charged device model (all pins)
Latch-up immunity 200 mA
1. All voltages values are measured with respect to the ground pin.
2. Differential voltage is the non-inverting input terminal with respect to the inverting input terminal.
3. The magnitude of input and output voltage must never exceed VCC +0.3 V.
4. Short-circuits can cause excessive heating. Destructive dissipation can result from short circuit on
amplifiers.
5. Human body model: a 100 pF capacitor is charged to the specified voltage, then discharged through a
1.5 kΩ resistor between two pins of the device. This is done for all couples of connected pin combinations
while the other pins are floating.
6. This is a minimum value. Machine model: a 200 pF capacitor is charged to the specified voltage, then
discharged directly between two pins of the device with no external series resistor (internal resistor < 5 Ω).
This is done for all couples of connected pin combinations while the other pins are floating.
7. Charged device model: all pins and package are charged together to the specified voltage and then
discharged directly to ground through only one pin. This is done for all pins.
Table 3. Operating conditions
(1)
(3)
(6)
(2)
(5)
(4)
(at T
amb
(7)
=25°C)
6V
±0.5 V
±2.5 V
830 mW
2
kV
0.5
200
V
60
1.5 kV
Symbol Parameter Value Unit
V
V
T
1. Tj must never exceed +150°C. P = (Tj - T
must dissipate in the application.
Supply voltage 4.5 to 5.5 V
CC
Common-mode input voltage
icm
Operating free-air temperature range
amb
4/22 Doc ID 15577 Rev 3
amb
/ R
(1)
= (Tj - T
thja
case
+1.5 V to
-V
CC
-1.5 V
+V
CC
-55 to +125 °C
) / R
with P the power that the RHF310
thjc
V
RHF310 Electrical characteristics
2 Electrical characteristics
Table 4. Electrical characteristics for VCC = ±2.5 V, T
amb
= 25° C
(unless otherwise specified)
Symbol Parameter Test conditions Min. Typ. Max. Unit
DC performance
+125°C -6.5 +6.5
V
Input offset voltage
io
-55°C -6.5 +6.5
+125°C 15
Non-inverting input bias current
I
ib+
-55°C 15
+125°C 7
Inverting input bias current
I
ib-
-55°C 7
+125°C 55
CMR
SVR
Common mode rejection ratio
20 log (ΔV
/ΔVio)
ic
Supply voltage rejection ratio
/ΔV
20 log (ΔV
CC
out
)
ΔVic = ±1 V
-55°C 55
+125°C 50
ΔVCC= 3.5V to 5V
-55°C 50
mV+25°C -6.5 1.7 +6.5
μA+25°C 3.1 12
μA+25°C 0.1 5
dB+25°C 57 61
dB+25°C 65 82
PSRR
I
Power supply rejection ratio
20 log (ΔVCC/ΔV
Supply current No load
CC
out
)
Dynamic performance and output characteristics
R
Transimpedance
OL
Small signal -3 dB bandwidth on
1k Ω load
Bw
Gain flatness at 0.1 dB
=200mVpp at
ΔV
CC
1kHz
+25°C 50 dB
+125°C 600
µA+25°C 400 530
-55°C 600
+125°C 500
ΔV
= ±1 V,
out
RL = 1 kΩ
kΩ+25°C 600 1450
-55°C 500
Rfb = 3 kΩ, AV = +1 +25°C 230
R
= 510 Ω, AV = +10 +25°C 26
fb
+125°C 70
Rfb = 3 kΩ, AV = +2
+25°C 70 120
MHz
-55°C 70
=20mV
V
out
AV = +2, RL = 1k Ω
pp
+25°C 25
Doc ID 15577 Rev 3 5/22
Electrical characteristics RHF310
Table 4. Electrical characteristics for VCC = ±2.5 V, T
amb
= 25° C
(unless otherwise specified) (continued)
Symbol Parameter Test conditions Min. Typ. Max. Unit
= 2 Vpp,
V
SR Slew rate
V
V
High level output voltage RL = 100 Ω
OH
Low level output voltage RL = 100 Ω
OL
(1)
I
sink
I
out
(2)
I
source
Output to GND
Noise and distortion
eN Equivalent input noise voltage
(3)
out
= +2, RL = 100 Ω
A
V
+25°C 115 V/μs
+125°C 1.5
+25°C 1.55 1.65
-55°C 1.5
+125°C -1.5
+25°C -1.66 -1.55
-55°C -1.5
+125°C 70
Output to GND
+25°C 70 110
-55°C 70
+125°C 60
+25°C 60 100
-55°C 60
F = 100 kHz +25°C 7.5 nV/√ Hz
V
V
mA
Equivalent positive input noise
(3)
current
F = 100 kHz +25°C 13 pA/√ Hz
iN
Equivalent negative input noise
(3)
current
F = 100 kHz +25°C 6 pA/√ Hz
AV = +2, V
RL = 100 Ω
SFDR Spurious free dynamic range
F = 1 MHz +25°C -87
F = 10 MHz +25°C -55
1. See Figure 10 for more details.
2. See Figure 11 for more details.
3. See Chapter 5 on page 15.
Table 5. Closed-loop gain and feedback components
Gain (V/V) + 2 - 2 + 4 - 4 + 10 - 10
(Ω) 1.2k 1k 150 300 100 180
R
fb
= 2 Vpp,
out
+25°C
dBc
6/22 Doc ID 15577 Rev 3
RHF310 Electrical characteristics
01234
-80
-70
-60
-50
-40
-30
-20
-10
0
H2
H3
Vcc=5V
F=10MHz
Load=1k
Ω
H2 and H3 (dBc)
Output (Vp-p)
Figure 1. Frequency response, positive gain Figure 2. Frequency response vs. capa-load
24
22
20
18
16
14
12
10
8
6
4
Gain (dB)
2
0
-2
-4
Small Signal
-6
Vcc=5V
-8
-10
1M 10M 100M
Load=1k
Ω
Gain=+10
Gain=+4
Gain=+2
Gain=+1
Frequency (Hz)
10
8
C-Load=10pF
R-iso=33 ohms
6
4
R-iso
R-iso
C-Load
C-Load
C-Load=22pF
R-iso=47ohms
Vout
Vout
1k
1k
2
0
Vin
Vin
+
-2
Gain (dB)
-4
+
-
-
3k
3k
3k
3k
-6
Gain=+2, Vcc=5V,
Gain=+2, Vcc=5V,
-8
Small Sig nal
Small Sig nal
-10
1M 10M 100M
Frequency (Hz)
C-Load=4.7pF
R-iso=0
Figure 3. Output amplitude vs. load Figure 4. Input voltage noise vs. frequency
4.0
3.5
Gain=32dB
Rg=12ohms
Rfb=510ohms
non-inverting input in short-circuit
Vcc=5V
3.0
2.5
Max output amplitude (Vp-p)
2.0
10 100 1k 10k 100k
Load (ohms)
Figure 5. Distortion at 1 MHz Figure 6. Distortion at 10 MHz
-20
Vcc=5V
-30
F=1MHz
Ω
Load=1k
-40
-50
-60
-70
H2
H2 and H3 (dBc)
-80
-90
-100
01234
H3
Output (Vp-p)
Doc ID 15577 Rev 3 7/22
Electrical characteristics RHF310
-40 -20 0 20 40 60 80 100 120
90
100
110
120
130
140
150
160
170
180
190
200
Gain=+2
Vcc=5V
Load=1k
Ω
Bw (MHz)
Temperature (°C)
Figure 7. Positive slew rate on 1 kΩ load Figure 8. Negative slew rate on 1 kΩ load
Figure 9. Quiescent current vs. V
400
200
Gain=+2
0
Vcc=5V
Inputs to ground, no load
Icc (micro-A)
-200
CC
Icc(+)
Figure 10. I
150
125
100
75
Isink (mA)
50
sink
-400
1.25 1.50 1.75 2.00 2.25 2.50
Figure 11. I
source
0
-25
-50
-75
Isource (mA)
-100
-125
-150
0.0 0.5 1.0 1.5 2.0
8/22 Doc ID 15577 Rev 3
+/-Vcc (V)
V (V)
Icc(-)
25
0
-2.0 -1.5 -1.0 -0.5 0.0
V (V)
Figure 12. Bandwidth vs. temperature
RHF310 Electrical characteristics
-40 -20 0 20 40 60 80 100 120
70
72
74
76
78
80
82
84
86
88
90
Vcc=5V
Load=1k
Ω
SVR (dB)
Temperature (°C)
-40 -20 0 20 40 60 80 100 120
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
Open Loop
Vcc=5V
Temperature ( C)
Vio (mV)
Figure 13. CMR vs. temperature Figure 14. SVR vs. temperature
66
64
62
60
CMR (dB)
58
Vcc=5V
Ω
Load=1k
56
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Figure 15. Slew rate vs. temperature Figure 16. ROL vs. temperature
140
130
120
110
100
SR (V/micro−s)
Gain=+2
90
Vcc=5V
Load=1k
80
-40 -20 0 20 40 60 80 100 120
neg. SR
pos. SR
Ω
Temperature (°C)
1.60
1.55
1.50
1.45
1.40
(M )
OL
R
1.35
1.30
1.25
Open Loop
Vcc=5V
1.20
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Figure 17. I
( A)
BIAS
I
vs. temperature Figure 18. Vio vs. temperature
bias
5
4
3
2
1
0
-1
-2
-3
Ib(+)
Ib(−)
Vcc=5V
-40 -20 0 20 40 60 80 100 120
Temperature (°C)
Doc ID 15577 Rev 3 9/22
Electrical characteristics RHF310
-40 -20 0 20 40 60 80 100 120
-300
-250
-200
-150
-100
-50
0
50
100
150
200
Output: short-circuit
Vcc=5V
Iout (mA)
Isource
Isink
Temperature (°C)
Figure 19. VOH and VOL vs. temperature Figure 20. I
2
VOH
1
0
(V)
-1
OH & OL
V
-2
-3
-4
Figure 21. I
400
200
-200
(micro A)
-400
CC
I
-600
-800
-1000
VOL
Gain=+2
Vcc=+/-2.5V
Ω
Load=1k
-40-200 20406080
Temperature (°C)
vs. temperature
CC
Icc(+)
0
Icc(-)
Gain=+2
Vcc=5V
no Load
in(+) and in(-) to GND
-40 -20 0 20 40 60 80 100 120
Temperature ( C)
vs. temperature
out
10/22 Doc ID 15577 Rev 3
RHF310 Power supply considerations
3 Power supply considerations
Correct power supply bypassing is very important for optimizing the performance of the
device in high-frequency ranges. The bypass capacitors should be placed as close as
possible to the IC pins to improve high-frequency bypassing. A capacitor greater than 1 µF
is necessary to minimize the distortion. For better quality bypassing, a capacitor of 10 nF
can be added, which should also be placed as close as possible to the IC pins. The bypass
capacitors must be incorporated for both the negative and positive supply.
Figure 22. Circuit for power supply bypassing
+V
CC
10 µF
+
10 nF
+
3.1 Single power supply
If you use a single-supply system, biasing is necessary to obtain a positive output dynamic
range between the 0 V and +V
amplifier provides an output swing from +0.9 V to +4.1 V on 1 kΩ loads.
The amplifier must be biased with a mid-supply (nominally +V
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 (55 µA maximum) as 1% of the current
through the resistance divider, two resistances of 470 Ω can be used to maintain a mid
supply.
-
-V
supply rails. Considering the values of VOH and VOL, the
CC
10 nF
10 µF
+
CC
AM00835
/2) in order to maintain the
CC
The input provides a high-pass filter with a break frequency below 10 Hz, which is
necessary to remove the original 0 V DC component of the input signal and to set it at
+V
/2.
CC
Figure 23 on page 12 illustrates a 5 V single power supply configuration.
A capacitor C
keep the right DC component at the output. C
is added in the gain network to ensure a unity gain at low frequencies to
G
contributes to a high-pass filter with Rfb//RG
G
and its value is calculated with a consideration of the cut-off frequency of this low-pass filter.
Doc ID 15577 Rev 3 11/22
Power supply considerations RHF310
Figure 23. Circuit for +5 V single supply
+5 V
10 µF
IN
+5 V
R1
470 Ω
R2
470 Ω
R
1 kΩ
+ 1 µF
in
10 nF
+
+
OUT
_
R
fb
R
G
C
G
1 kΩ
AM00841
12/22 Doc ID 15577 Rev 3
RHF310 Noise measurements
4 Noise measurements
The noise model is shown in Figure 24.
● eN: input voltage noise of the amplifier.
● iNn: negative input current noise of the amplifier.
● iNp: positive input current noise of the amplifier.
Figure 24. Noise model
+
+
R3
N3
iN
_
eN
-
iN
Output
HP3577
Input noise:
8 nV/√Hz
R1
N2
R2
N1
AM00837
The thermal noise of a resistance R is:
4kTRΔF
where ΔF is the specified bandwidth, and k is the Boltzmann's constant, equal to
1,374.10-23J/°K. T is the temperature (°K).
On a 1 Hz bandwidth the thermal noise is reduced to:
4kTR
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.
Equation 1
eNo V12V22V32V42V52V6
+++++=
2
Doc ID 15577 Rev 3 13/22
Noise measurements RHF310
Equation 2
eNo2eN2g2iNn2R22iNp
+×+× R3
2
× g2×
2
2
R2
------- -
4kTR1 4kTR2 1
R1
The input noise of the instrumentation must be extracted from the measured noise value.
The real output noise value of the driver is:
Equation 3
2
instrumentation()
eNo Measured()
–=
2
The input noise is called equivalent input noise because 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 fifth terms of Equation 2, you obtain:
Equation 4
eNo2eN2g2iNn2R22iNp
2
+×+× R32× g2× g4kTR21
4.1 Measurement of the input voltage noise eN
Assuming a short-circuit on the non-inverting input (R3=0), from Equation 4 you can derive:
R2
------- -+
R1
2
R2
------- -+
4kTR3×++×+=
R1
2
4kTR3×+×+=
Equation 5
eNo eN
2g2
iNn2R22g4kTR2×+×+×=
To easily extract the value of eN, the resistance R2 must be as low as possible. On the other
hand, the gain must be high enough.
R3=0, gain: g=100
4.2 Measurement of the negative input current noise iNn
To measure the negative input current noise iNn, R3 is set to zero and Equation 5 is used.
This time, the gain must be lower in order to decrease the thermal noise contribution.
R3=0, gain: g=10
4.3 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 selected so as to keep its thermal noise contribution as low as possible
against the iNp contribution.
R3=100 Ω, gain: g=10
14/22 Doc ID 15577 Rev 3
RHF310 Intermodulation distortion product
5 Intermodulation distortion product
The non-ideal output of the amplifier can be described by the following series of equations.
V
outC0C1VinC2
++ +=
V
2
in
… C+nV
n
in
where the input is Vin= Asinωt, C0 is the DC component, C1(Vin) is the fundamental and C
is the amplitude of the harmonics of the output signal V
out
.
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:
VinA ω1tsin A ω2tsin+=
therefore:
V
outC0C1
A ω1tsin A ω2tsin+()C2A ω1tsin A ω2tsin+()
++ +=
2
… CnA ω1tsin A ω2tsin+()
n
From this expression, we can extract the distortion terms and the intermodulation terms
from a single sine wave.
● Second-order intermodulation terms IM2 by the frequencies (ω
an amplitude of C2A
2
.
● Third-order intermodulation terms IM3 by the frequencies (2ω
ω
+2ω2) and (ω1+2ω2) with an amplitude of (3/4)C3A3.
1
) and (ω1+ω2) with
1-ω2
), (2ω1+ω2), (−
1-ω2
The intermodulation product of the driver is measured by using the driver as a mixer in a
summing amplifier configuration (Figure 25). In this way, the non-linearity problem of an
external mixing device is avoided.
n
Doc ID 15577 Rev 3 15/22
Intermodulation distortion product RHF310
Figure 25. Inverting summing amplifier
V
in1
V
in2
R
1
R
2
R
fb
_
V
out
+
1 kΩ
R
AM00842
16/22 Doc ID 15577 Rev 3
RHF310 Bias of an inverting amplifier
6 Bias of an inverting amplifier
A resistance is necessary to achieve good input biasing, such as resistance R shown in
Figure 26.
The value of this resistance is calculated from the negative and positive input bias current.
The aim is to compensate for the offset bias current, which can affect the input offset voltage
and the output DC component. Assuming I
R is:
R
Figure 26. Compensation of the input bias current
R
-
I
ib
in
_
, I
ib-
R
×
inRfb
-----------------------=
R
in
R
, Rin, Rfb and a 0 V output, the resistance
ib+
R+
fb
fb
VCC+
Output
+
+
I
ib
-
V
CC
Load
R
AM00839
Doc ID 15577 Rev 3 17/22
Active filtering RHF310
7 Active filtering
Figure 27. Low-pass active filtering, Sallen-Key
C1
1
R
IN
2
R
+
C2
_
R
fb
From the resistors R
R
G
and RG it is possible to directly calculate the gain of the filter in a
fb
classic non-inverting amplification configuration.
R
AVg1
fb
--------+==
R
g
The response of the system is assumed to be:
Vout
----------------- -
Vin
jω
jω
-------------------------------------------==
12ζ
T
jω
------
ω
jω
g
c
jω()
------------ -++
2
ω
c
2
The cut-off frequency is not gain-dependent and so becomes:
OUT
1 kΩ
AM00843
The damping factor is calculated using the following expression.
1
-- -
ζ
ωcC1R1C1R2C2R1C1R1g–++()=
2
The higher the gain, the more sensitive the damping factor. When the gain is higher than 1,
it is preferable to use very stable resistor and capacitor values. In the case of R1=R2=R:
Due to a limited selection of capacitor values in comparison with the resistors, you can set
18/22 Doc ID 15577 Rev 3
C1=C2=C, so that:
ω
c
ζ
ζ
1
------------------------------------ -=
R1R2C1C2
2C
–
2C1
-------------------------------- -=
2C1C
2R2R
–
1
-------------------------------- -=
2R1R
R
--------
R
2
R
--------
R
2
fb
g
fb
g
RHF310 Package information
8 Package information
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK
®
packages, depending on their level of environmental compliance. ECOPACK®
®
is an ST trademark.
Doc ID 15577 Rev 3 19/22
Package information RHF310
8.1 Ceramic Flat-8 package information
Figure 28. Ceramic Flat-8 package mechanical drawing
Note: The upper metallic lid is not electrically connected to any pins, nor to the IC die inside the
package. Connecting unused pins or metal lid to ground or to the power supply will not affect
the electrical characteristics.
Table 6. Ceramic Flat-8 package mechanical data
Dimensions
Ref.
Min. Typ. Max. Min. Typ. Max.
A 2.24 2.44 2.64 0.088 0.096 0.104
b 0.38 0.43 0.48 0.015 0.017 0.019
c 0.10 0.13 0.16 0.004 0.005 0.006
D 6.35 6.48 6.61 0.250 0.255 0.260
E 6.35 6.48 6.61 0.250 0.255 0.260
E2 4.32 4.45 4.58 0.170 0.175 0.180
E3 0.88 1.01 1.14 0.035 0.040 0.045
e 1.27 0.050
L 3.00 0.118
Q 0.66 0.79 0.92 0.026 0.031 0.092
S1 0.92 1.12 1.32 0.036 0.044 0.052
Millimeters Inches
N08 08
20/22 Doc ID 15577 Rev 3
RHF310 Revision history
9 Revision history
Table 7. Document revision history
Date Revision Changes
26-May-2009 1 Initial release.
Added Mass in Features on cover page.
Added Table 1: Device summary on cover page, with full
12-Jul-2010 2
27-Jul-2011 3
ordering information.
Updated temperature limits for T
min
< T
amb
< T
max
in
Table 3: Operating conditions.
Added Note: on page 20 and in the "Pin connections" diagram
on the coverpage.
Doc ID 15577 Rev 3 21/22
RHF310
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22/22 Doc ID 15577 Rev 3
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