The RHF330 is a current feedback operational
amplifier that uses very high-speed
complementary technology to provide a large
bandwidth of 1 GHz in gains of 2 while drawing
only 16.6 mA of quiescent current. The RHF330
also offers 0.1 dB gain flatness up to 160 MHz
with a gain of 2. With a slew rate of 1800 V/µs and
an output stage optimized for standard 100 Ω
loads, this device is highly suitable for
applications where speed and low distortion are
the main requirements. The device is a single
operator available in a Flat-8 hermetic ceramic
package, saving board space as well as providing
excellent thermal and dynamic performance.
Order codeSMD pinQuality levelPackage Lead finishMarkingEPPL Packing
RHF330Absolute maximum ratings and operating conditions
1 Absolute maximum ratings and operating conditions
Table 2.Absolute maximum ratings
SymbolParameterValueUnit
V
CC
V
id
V
in
T
stg
T
R
thja
R
thjc
P
max
ESD
Supply voltage
Differential input voltage
Input voltage range
Storage temperature-65 to +150°C
Maximum junction temperature150°C
j
Flat-8 thermal resistance junction to ambient 50°C/W
Flat-8 thermal resistance junction to case 30°C/W
Flat-8 maximum power dissipation
(T
= + 25° C) for Tj=150°C
amb
HBM: human body model
pins 1, 4, 5, 6, 7 and 8
pins 2 and 3
MM: machine model
pins 1, 4, 5, 6, 7 and 8
pins 2 and 3
CDM: charged device model
pins 1, 4, 5, 6, 7 and 8
pins 2 and 3
Latch-up immunity200mA
(1)
(3)
(6)
6V
(2)
± 0.5V
± 2.5V
(4)
(5)
830mW
2
kV
0.6
200
V
80
(7)
1.5
kV
1
1. All voltage 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-circuits on all
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 < 5Ω). 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.
Table 3.Operating conditions
SymbolParameterValueUnit
V
V
T
amb
1. Tj must never exceed +150°C. P = (Tj - Tamb)/Rthja = (Tj - Tcase)/Rthjc with P being the power that the
RHF330 must dissipate in the application.
Supply voltage 4.5 to 5.5V
CC
Common-mode input voltage-V
icm
Operating free-air temperature range
(1)
+1.5 to +VCC-1.5V
CC
-55 to +125°C
Doc ID 15576 Rev 33/22
Page 4
Electrical characteristicsRHF330
2 Electrical characteristics
Table 4.Electrical characteristics for VCC= ±2.5 V, T
Figure 1.Frequency response, positive gain Figure 2.Flatness, gain = +2 compensated
24
22
20
18
16
14
12
10
8
6
4
Gain (dB)
2
0
-2
-4
Small Signal
-6
Vcc=5V
-8
Load=100
-10
1M10M100M1G
Gain=10
Gain=4
Gain=2
Gain=1
Ω
Frequency (Hz)
6.5
Vin
6.4
0.5pF
6.3
6.2
Gain=+2, Vcc=+5V,
Small Signal
6.1
Gain (dB)
Vout
+
-
100
300
300
6.0
5.9
5.8
1M10M100M1G
Frequency (Hz)
Figure 3.Flatness, gain = +4 compensatedFigure 4.Flatness, gain = +10 compensated
12.2
12.1
12.0
11.9
11.8
11.7
Vin
11.6
Gain (dB)
11.5
2.7pF
11.4
11.3
Gain=+4, Vcc=+5V,
Small Signal
11.2
1M10M100M1G
Vout
+
-
100
240
82
Frequency (Hz)
20.3
20.2
20.1
20.0
19.9
19.8
Vin
19.7
Gain (dB)
19.6
12pF
19.5
19.4
Gain=+10, Vcc=+5V,
Small Signal
19.3
1M10M100M1G
Vout
+
-
100
200
22
Frequency (Hz)
Figure 5.Quiescent current vs. V
CC
Figure 6.Positive slew rate
20
15
10
Icc(+)
5
0
Icc (mA)
-5
-10
-15
Gain=+2
Input to ground, no load
-20
0.00.51.01.52.02.5
+/- Vcc (V)
Icc(-)
6/22 Doc ID 15576 Rev 3
Page 7
RHF330Electrical characteristics
Figure 7.Negative slew rateFigure 8.Output amplitude vs. load
2.00
1.75
1.50
1.25
1.00
0.75
0.50
Output Response (V)
0.25
0.00
-2ns-1ns0s1ns2ns
Gain=+2
Vcc=+5V
Load=100
Ω
Time (ns)
Figure 9.Distortion vs. amplitudeFigure 10. I
Gain=+2
Vcc=+5V
F=10MHz
Ω
Load=100
HD2
HD3
sink
V (V)
Figure 11. I
600
550
500
450
400
350
300
250
Isink (mA)
200
150
100
50
0
-2.0-1.5-1.0-0.50.0
4.0
3.5
3.0
2.5
Max. Output Amplitude (Vp-p)
2.0
101001k10k100k
Load (ohms)
source
0
-50
-100
-150
-200
-250
-300
-350
Isource (mA)
-400
-450
-500
-550
-600
0.00.51.01.52.0
V (V)
Figure 12. Noise figure
Gain=+2
Vcc=5V
Ω
Load=100
Vcc=5V
Doc ID 15576 Rev 37/22
Page 8
Electrical characteristicsRHF330
Gain=37dB
Rg=10ohms
Rfb=750ohms
non-inverting input in short-circuit
Vcc=5V
-40-20020406080100120
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Output: short-circuit
Vcc=5V
Iout (A)
Isource
Isink
Temperature (°C)
-40-20020406080100120
50
55
60
65
70
75
80
85
Gain=+1
Vcc=5V
Load=100
Ω
SVR (dB)
Temperature (°C)
Figure 13. Input current noise vs. frequencyFigure 14. Input voltage noise vs. frequency
Gain=14.1dB
Rg=180ohms
Rfb=750ohms
Neg. Current
Noise
Pos. Current
Noise
Figure 15. Reverse isolation vs. frequencyFigure 16. I
0
-20
-40
non-inverting input in short-circuit
Vcc=5V
vs. temperature
out
-60
Gain (dB)
-80
Small Signal
Vcc=5V
Ω
Load=100
-100
1M10M100M1G
Figure 17. CMR vs. temperatureFigure 18. SVR vs. temperature
60
58
56
54
52
CMR (dB)
50
48
Vcc=5V
46
8/22 Doc ID 15576 Rev 3
Ω
Load=100
-40-20020406080100120
Frequency (Hz)
Temperature (°C)
Page 9
RHF330Electrical characteristics
-40-200 20406080
-4
-3
-2
-1
0
1
2
Gain=+2
Vcc=5V
Load=100
Ω
VOL
VOH
V
OH & OL
(V)
Temperature (°C)
-40-20020406080100120
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
20
Gain=+2
Vcc=5V
no Load
In+/In- to GND
Icc(+)
Icc(-)
Temperature ( C)
I
CC
(mA)
Figure 19. ROL vs. temperatureFigure 20. VOH and VOL vs. temperature
180
160
140
(M )
OL
120
R
100
Open Loop
Vcc=5V
80
-40-20020406080100120
Figure 21. I
30
28
26
24
22
20
18
16
I bias ( A)
14
12
10
8
Vcc=5V
Load=100
6
-40-20020406080100120
bias
Ib(+)
Ib(−)
Temperature (°C)
vs. temperatureFigure 22.ICC vs. temperature
Ω
Temperature (°C)
Figure 23. V
1000
800
600
(micro V)
IO
400
V
200
0
vs. temperature
io
Open Loop
Vcc=5V
Ω
Load=100
-40-20020406080100120
Temperature ( C)
Doc ID 15576 Rev 39/22
Page 10
Demonstration board schematicsRHF330
3 Demonstration board schematics
Figure 24. Electrical schematics (inverting and non-inverting gain configurations)
Figure 25. RHF3xx demonstration board
10/22 Doc ID 15576 Rev 3
Page 11
RHF330Demonstration board schematics
Figure 26. Top view layout
Figure 27. Bottom view layout
Doc ID 15576 Rev 311/22
Page 12
Power supply considerationsRHF330
4 Power supply considerations
Correct power supply bypassing is very important for optimizing performance in highfrequency 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 10 nF capacitor can be added. It
should also be placed as close as possible to the IC pins. The bypass capacitors must be
incorporated for both the negative and the positive supply.
For example, on the RHF3xx single op-amp demonstration board, these capacitors are C6,
C7, C8, C9.
Figure 28. Circuit for power supply bypassing
+V
CC
10 µF
+
10 nF
+
4.1 Single power supply
In the event that a single supply system is used, biasing is necessary to obtain a positive
output dynamic range between 0 V and +V
and V
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, to keep a stable mid-supply, two resistances of 470 Ω can be
used.
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
Figure 29 on page 13 illustrates a 5 V single power supply configuration for the RHF3xx
single op-amp demonstration board.
, the amplifier provides an output swing from +0.9 V to +4.1 V on a 100 Ω load.
OL
-
-V
supply rails. Considering the values of VOH
CC
10 nF
10 µF
+
CC
AM00835
/2), in order to maintain the
CC
CC
/2.
12/22 Doc ID 15576 Rev 3
Page 13
RHF330Power supply considerations
A capacitor CG is added in the gain network to ensure a unity gain at low frequencies to
keep the right DC component at the output. C
contributes to a high-pass filter with Rfb//RG
G
and its value is calculated with regard to the cut-off frequency of this low-pass filter.
Figure 29. 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
+
+
_
R
fb
R
G
C
G
100 µ F
OUT
100 Ω
AM00836
Doc ID 15576 Rev 313/22
Page 14
Noise measurementsRHF330
5 Noise measurements
The noise model is shown in Figure 30.
●eN: input voltage noise of the amplifier
●iNn: negative input current noise of the amplifier
●iNp: positive input current noise of the amplifier
Figure 30. Noise model
+
R3
N3
iN
iN
+
_
eN
-
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.
On a 1 Hz bandwidth the thermal noise is reduced to:
4kTR
where k is the Boltzmann's constant, equal to 1,374.E(-23)J/°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.
Equation 1
eNoV12V22V32V42V52V6
+++++=
2
14/22 Doc ID 15576 Rev 3
Page 15
RHF330Noise measurements
Equation 2
2
eNo2eN2g2iNn2R22iNp
+×+×R3
2
×g2×
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()
eNoMeasured()
–=
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 the fifth term of Equation 2 we obtain:
Equation 4
2
eNo2eN2g2iNn2R22iNp
+×+×R3
2
×g2×g4kTR21
5.1 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:
2
R2
------- -+
4kTR3×++×+=
R1
2
2
R2
------- -+
4kTR3×+×+=
R1
Equation 5
eNoeN
2g2
iNn2R22g4kTR2×+×+×=
To easily extract the value of eN, the resistance R2 is as low as possible. On the other hand,
the gain must be large enough.
R3=0, gain: g=100
5.2 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 to decrease the thermal noise contribution.
R3=0, gain: g=10
5.3 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 chosen so that its thermal noise contribution is as low as possible
against the iNp contribution.
R3=100 W, gain: g=10
Doc ID 15576 Rev 315/22
Page 16
Intermodulation distortion productRHF330
6 Intermodulation distortion product
The non-ideal output of the amplifier can be described by the following series of equations.
2
Where the input is V
V
=Asinωt, C0 is the DC component, C1(Vin) is the fundamental and C
in
C0C1VinC2V
out
++ +=
the amplitude of the harmonics of the output signal V
in
out
… C+nV
n
in
is
n
.
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:
VinAω1tsinAω2tsin+=
Then:
C0C1Aω1tsinAω2tsin+()C2Aω1tsinAω2tsin+()
V
out
+++=
2
… CnAω1tsinAω2tsin+()
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
amplitude of C2A
●Third order intermodulation terms IM3 by the frequencies (2ω
and (ω
+2ω2) with an amplitude of (3/4)C3A3.
1
2
.
) and (ω1+ω2) with an
1-ω2
), (2ω1+ω2), (−ω1+2ω2)
1-ω2
The intermodulation product of the driver is measured by using the driver as a mixer in a
summing amplifier configuration (Figure 31 on page 17). In this way, the non-linearity
problem of an external mixing device is avoided.
16/22 Doc ID 15576 Rev 3
Page 17
RHF330Intermodulation distortion product
Figure 31. Inverting summing amplifier
V
in1
V
in2
R
1
R
2
R
fb
_
V
out
+
100 Ω
R
AM00838
Doc ID 15576 Rev 317/22
Page 18
Bias of an inverting amplifierRHF330
7 Bias of an inverting amplifier
A resistance is necessary to achieve good input biasing, such as resistance R shown in
Figure 32.
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
resistance R is:
Figure 32. Compensation of the input bias current
R
-
I
ib
in
, I
, Rin, Rfb and a zero volt output, the
ib-
ib+
R
×
inRfb
R
------------------------=
R
R+
in
fb
R
fb
_
VCC+
Output
+
+
I
ib
-
V
CC
Load
R
AM00839
18/22 Doc ID 15576 Rev 3
Page 19
RHF330Active filtering
8 Active filtering
Figure 33. Low-pass active filtering, Sallen-Key
C1
1
R
IN
2
R
C2
+
OUT
_
R
fb
From the resistors R
R
G
and RG we can directly calculate the gain of the filter in a classic non-
fb
inverting amplification configuration.
R
AVg1
fb
--------+==
R
g
We assume the following expression is the response of the system.
Vout
---------------- -
Vin
jω
jω
T
jω
---------------------------------------- -==
12ζ
g
jω
-----
ω
2
jω()
----------- -++
2
c
ω
c
The cut-off frequency is not gain-dependent and so becomes:
100 Ω
AM00840
ω
c
1
------------------------------------ -=
R1R2C1C2
The damping factor is calculated by the following expression.
1
-- -
ζ
ωcC1R1C1R2C2R1C1R1g–++()=
2
The higher the gain, the more sensitive the damping factor is. 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:
R
fb
–
2C1
2C1C
--------
R
2
g
2C
ζ
-------------------------------- -=
Due to a limited selection of capacitor values in comparison with the resistors, we can set
C1=C2=C, so that:
2R
ζ
-------------------------------- -=
Doc ID 15576 Rev 319/22
–
2R1
2R
1R2
R
--------
R
fb
g
Page 20
Package informationRHF330
9 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®
Modified temperature limits in Ta b le 4 .
Changed order codes in Ta b le 7 .
Added Mass in Features on cover page.
Added full ordering information in Ta bl e 1 .
Doc ID 15576 Rev 321/22
Page 22
RHF330
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