CLC452
Single Supply, Low Power, High Output, Current
Feedback Amplifier
General Description
The CLC452 has a new output stage that delivers high
output drive current (100mA), but consumes minimal
quiescent supply current (3.0mA) from a single 5V supply. Its
current feedback architecture, fabricated in an advanced
complementary bipolar process, maintains consistent
performance over a wide range of gains and signal levels,
and has a linear-phase response up to one half of the −3dB
frequency.
The CLC452 offers superior dynamic performance with a
130MHz small signal bandwidth, 400V/µs slew rate and
4.5ns rise/fall times (2VSTEP. The combination of low
quiescent power, high output current drive, and high speed
performance make the CLC452 well suited for many battery
powered personal communication/computing systems.
The ability to drive low impedance, high capacitive loads,
makes the CLC452 ideal for single ended cable applications.
It also drives low impedance loads with minimum distortion.
The CLC452 will drive a 100Ω load with only −75/−74dBc
second/third harmonic distortion (AV = +2, VOUT = 2VPP, f
=1MHz). With a 25Ω load, and the same conditions, it
produces only −65/−77dBc second/third harmonic distortion.
It is also optimized for driving high currents into single-ended
transformers and coils.
When driving the input of high resolution A/D converters, the
CLC452 provides excellent −78/−85dBc second/third
harmonic distortion (AV = +2, VOUT = 2VPP, f =1MHz, RL =
1kΩ) and fast settling time.
Available in SOT23-5, the CLC452 is ideal for applications
where space is critical.
n
n
n
n
n
n
−78/−85dBc HD2/HD3 (1MHz)
25ns settling to 0.05%
400V/µs slew rate
Stable for capacitive loads up to 1000pF
Single 5V to ± 5V supplies
Available in Tiny SOT23-5 package
Applications
n
n
n
n
n
n
n
Coaxial cable driver
Twisted pair driver
Transformer/Coil Driver
High capacitive load driver
Video line driver
Portable/battery powered applications
A/D driver
Maximum Output Voltage vs. RL
Features
n 100mA output current
n 3.0mA supply current
n 130MHz bandwidth (AV = +2)
DS012790-1
Connection Diagrams
DS012790-4
DS012790-5
Pinout
SOT23-5
Pinout
DIP & SOIC
© 2001 National Semiconductor Corporation
DS012790
www.national.com
CLC452 Single Supply, Low Power, High Output, Current Feedback Amplifier
March 2001
CLC452
Typical Application
DS012790-2
Single Supply Cable Driver
DS012790-3
Response After 10m of Cable
Ordering Information
Package
Temperature Range
Industrial
Part Number
Package Marking
NSC Drawing
8-pin plastic DIP
−40˚C to +85˚C
CLC452AJP
CLC452AJP
N08E
8-pin plastic SOIC
−40˚C to +85˚C
CLC452AJE
CLC452AJE
M08A
5-pin SOT
−40˚C to +85˚C
CLC452AJM5
A21
MA05A
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2
Lead Solder Duration (+300˚C)
ESD Rating (human body model)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Supply Voltage (VCC-(VEE)
Output Current (see note 3)
Common Mode Input Voltage
Maximum Junction Temperature
Storage Operating Temperature
Range
10 sec
500V
Operating Ratings
+14V
140mA
VEE to VCC
+150˚C
Thermal Resistance
Package
MDIP
SOIC
SOT23
−65˚C to +150˚C
(θJC)
105˚C/W
95˚C/W
140˚C/W
(θJA)
155˚C/W
175˚C/W
210˚C/W
+5V Electrical Characteristics
AV = +2, VS = +5V(Note 5), VCM = VEE + (VS/2), RL = 100Ω, Rf = 1kΩ, RL tied to VCM; unless specified
Symbol
Parameter
Ambient Temperature
Conditions
CLC452AJ
Typ
Min/Max (Note 2)
Units
+25˚C
+25˚C
0 to
70˚C
−40 to
85˚C
VO < 0.5VPP
130
95
90
85
MHz
VO < 2.0VPP
VO < 0.5VPP
< 200MHz, VO < 0.5VPP
< 30MHz VO < 0.5VPP
< 30MHz, VO = 0.5VPP
95
80
77
75
MHz
30
25
20
20
MHz
0
0.5
0.9
1.0
dB
0.1
0.3
0.3
0.3
dB
0.1
0.2
0.3
0.3
deg
6.0
6.4
6.8
ns
ns
Frequency Domain Response
-3dB Bandwidth
−0.1dB Bandwidth
Gain Peaking
Gain Rolloff
linear phase deviation
TIME DOMAIN RESPONSE
Rise and Fall Time
2V Step
4.5
Settling Time to ± 0.05%
1V Step
25
-
-
-
Overshoot
2V Step
11
15
18
18
%
Slew Rate
2V Step
400
300
275
260
V/µs
DISTORTION AND NOISE RESPONSE
2nd Harmonic Distortion
3rd Harmonic Distortion
2VPP, 1MHz
−75
−69
−67
−67
dBc
2VPP,1MHz RL = 1kΩ
−78
−70
−68
−68
dBc
2VPP, 5MHz
−65
−58
−56
−56
dBc
dBc
2VPP, 1MHz
−74
−70
−68
−68
2VPP, 1MHz RL =1kΩ
−85
−75
−73
−73
dBc
2VPP, 5MHz
−60
−55
−53
−53
dBc
Voltage (eni)
> 1MHz
2.8
3.5
3.8
3.8
nV/
Non-Inverting Current (ibn)
> 1MHz
7.5
10
11
11
pA/
Non-Inverting Current (ibi)
> 1MHz
10.5
14
15
15
pA/
1
4
6
6
mV
Equivalent Input Noise
Static, DC Performance
Input Offset Voltage (Note 4)
Average Drift
Input Bias Current
(non-inverting) (Note 4)
Average Drift
Input Bias Current (inverting)
(Note 4)
Average Drift
8
-
-
-
µV/˚C
6
18
22
24
µA
40
-
-
-
nA/˚C
6
14
16
17
µA
25
-
-
-
nA/˚C
Power Supply Rejection Ratio
DC
48
45
43
43
dB
Common-Mode Rejection Ratio
DC
51
48
46
46
dB
3
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CLC452
Absolute Maximum Ratings (Note 1)
CLC452
+5V Electrical Characteristics
(Continued)
AV = +2, VS = +5V(Note 5), VCM = VEE + (VS/2), RL = 100Ω, Rf = 1kΩ, RL tied to VCM; unless specified
Symbol
Parameter
Conditions
Typ
Min/Max (Note 2)
Units
Static, DC Performance
Supply Current (Note 4)
RL = ∞
3.0
3.4
3.6
3.6
mA
Input Resistance (non-inverting)
0.39
0.28
0.25
0.25
MΩ
Input Capacitance
(non-inverting)
1.5
2.3
2.3
2.3
pF
Input Voltage Range, High
4.2
4.1
4.0
4.0
V
Miscellaneous Performance
Input Voltage Range, Low
0.8
0.9
1.0
1.0
V
Output Voltage Range, High
RL = 100Ω
4.0
3.9
3.8
3.8
V
Output Voltage Range, Low
RL = 100Ω
1.0
1.1
1.2
1.2
V
Output Voltage Range, High
RL = ∞
RL = ∞
4.1
4.0
4.0
3.9
V
0.9
1.0
1.0
1.1
V
100
80
65
40
mA
70
105
105
140
mΩ
Output Voltage Range, Low
Output Current (Note 3)
Output Resistance, Closed Loop
DC
± 5V Electrical Characteristics
AV = +2, VCC = ± 5V, RL =100Ω, Rf = 1kΩ; unless specified
Symbol
Parameter
Ambient Temperature
Conditions
CLC452AJ
Typ
Min/Max(Note 2)
Units
+25˚C
+25˚C
0 to
70˚C
−40 to
85˚C
VO < 1.0VPP
160
135
120
115
MHz
VO < 4.0VPP
75
60
57
55
MHz
−0.1dB Bandwidth
VO < 1.0VPP
30
25
25
20
MHz
Gain Peaking
< 200MHz, VO < 1.0VPP
< 30MHz, VO < 1.0VPP
< 30MHz, VO < 1.0VPP)
0
0.5
0.9
1.0
dB
0.1
0.2
0.3
0.3
dB
0.1
0.2
0.3
0.3
deg
Differential Gain
NTSC, RL = 150Ω
0.05
-
-
-
%
Differential Phase
NTSC, RL = 150Ω
0.08
-
-
-
deg
Rise and Fall Time
2V Step
3.2
4.2
4.5
5.0
ns
ns
Frequency Domain Response
-3dB Bandwidth
Gain Rolloff
Linear Phase Deviation
TIME DOMAIN RESPONSE
Settling Time to ± 0.05%
2V Step
20
-
-
-
Overshoot
2V Step
8
12
15
15
%
Slew Rate
2V Step
540
400
370
350
V/µs
DISTORTION AND NOISE RESPONSE
2nd Harmonic Distortion
3rd Harmonic Distortion
2VPP,1MHz
−77
−71
−69
−69
dBc
2VPP,1MHz, RL = 1kΩ
−78
−72
−70
−70
dBc
2VPP,5MHz
−69
−63
−61
−61
dBc
2VPP, 1MHz
−72
−68
−66
−66
dBc
2VPP, 1MHz, RL = 1kΩ
−90
−80
−78
−78
dBc
2VPP, 5MHz
−58
−54
−52
−52
dBc
Voltage (eni)
> 1MHz
2.8
3.5
3.8
3.8
nV/
Non-Inverting current (ibn)
> 1MHz
7.5
10
11
11
pA/
Inverting Current (ibi)
> 1MHz
10.5
14
15
15
pA/
Equivalent Input Noise
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4
CLC452
± 5V Electrical Characteristics
(Continued)
AV = +2, VCC = ± 5V, RL =100Ω, Rf = 1kΩ; unless specified
Symbol
Parameter
Conditions
Typ
Min/Max(Note 2)
Units
Static, DC Performance
Input Offset Voltage
1
6
8
8
mV
Average Drift
10
-
-
-
µV/˚C
Input Bias Current
(non-inverting)
3
18
23
25
µA
Average Drift
40
-
-
-
nA/˚C
13
24
31
31
µA
Input Bias Current (inverting)
30
-
-
-
nA/˚C
Power Supply Rejection Ratio
Average Drift
DC
48
45
43
43
dB
Common-Mode Rejection Ratio
DC
53
50
48
48
dB
Supply Current
RL = ∞
3.2
3.8
4.0
4.0
mA
Input Resistance (non-inverting)
0.52
0.35
0.30
0.30
MΩ
Input Capacitance
(non-inverting)
1.2
1.8
1.8
1.8
pF
± 4.2
± 3.8
± 4.0
± 4.1
± 3.6
± 3.8
± 4.1
± 3.6
± 3.8
± 4.0
± 3.5
± 3.7
V
130
100
80
50
mA
60
90
90
120
mΩ
Miscellaneous Performance
Common-Mode Input Range
Output Voltage Range
RL = 100Ω
Output Voltage Range
RL = ∞
Output Current (Note 3)
Output Resistance, Closed Loop
DC
V
V
Note 1: “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the devices
should be operated at these limits. The table of “Electrical Characteristics” specifies conditions of device operation.
Note 2: Min/max ratings are based on product characterization and simulation. Individual parameters are tested as noted. Outgoing quality levels are determined
from tested parameters.
Note 3: The short circuit current can exceed the maximum safe output current.
Note 4: AJ-level: spec. is 100% tested at +25˚C.
Note 5: VS = VCC − VEE
+5V Typical Performance Characteristics
Non-Inverting Frequency Response
Inverting Frequency Response
DS012790-6
DS012790-7
5
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Frequency Response vs. RL
(Continued)
Frequency Response vs. VO
DS012790-8
Frequency Response vs. CL
DS012790-9
Open Loop Transimpedance Gain, Z(s)
DS012790-10
Gain Flatness
DS012790-11
Equivalent Input Noise
Magnitude (0.05dB/div)
CLC452
+5V Typical Performance Characteristics
10
20
30
Frequency (MHz)
DS012790-12
DS012790-13
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6
2nd & 3rd Harmonic Distortion
CLC452
+5V Typical Performance Characteristics
(Continued)
2nd Harmonic Distortion, RL = 25Ω
-44
Distortion (dBc)
-46
10MHz
-48
5MHz
-50
-52
-54
2MHz
-56
-58
1MHz
-60
0
0.5
1
1.5
2
2.5
Output Amplitude (Vpp)
DS012790-15
DS012790-14
3rd Harmonic Distortion, RL = 25Ω
2nd Harmonic Distortion, RL = 100Ω
-35
Distortion (dBc)
-40
10MHz
-45
5MHz
-50
-55
2MHz
-60
1MHz
-65
-70
-75
0
0.5
1
1.5
2
2.5
Output Amplitude (Vpp)
DS012790-16
DS012790-17
3rd Harmonic Distortion, RL = 100Ω
2nd Harmonic Distortion, RL = 1kΩ
-45
Distortion (dBc)
-50
10MHz
-55
5MHz
-60
-65
2MHz
-70
1MHz
-75
-80
0
0.5
1
1.5
2
2.5
Output Amplitude (Vpp)
DS012790-18
DS012790-19
7
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3rd Harmonic Distortion, RL = 1kΩ
(Continued)
Closed Loop Output Resistance
DS012790-20
Recommended RS vs. CL
DS012790-21
Large & Small Signal Pulse Response
DS012790-23
DS012790-22
PSRR & CMRR
IBN, VOS vs. Temperature
-0.6
6
-0.7
IBN
5
Vos
-0.8
4
-0.9
3
-1
2
-1.1
IBN (µA)
Offset Voltage Vos (mV)
CLC452
+5V Typical Performance Characteristics
1
-100
-50
0
50
100
150
Temperature (ϒC)
DS012790-25
DS012790-24
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8
CLC452
+5V Typical Performance Characteristics
(Continued)
Maximum Output Voltage vs. RL
DS012790-26
± 5V Typical Performance Characteristics
Non-Inverting Frequency Response
Inverting Frequency Response
DS012790-27
Frequency Response vs. RL
DS012790-28
Frequency Response vs. VO
DS012790-29
DS012790-30
9
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Frequency Response vs. CL
(Continued)
Magnitude (0.05dB/div)
Gain Flatness
5
0
10
20
15
25
30
Frequency (MHz)
DS012790-32
DS012790-31
Small Signal Pulse Response
Large Signal Pulse Response
DS012790-33
2nd & 3rd Harmonic Distortion
DS012790-34
2nd Harmonic Distortion, RL = 25Ω
-40
Distortion (dBc)
CLC452
± 5V Typical Performance Characteristics
-45
10MHz
-50
5MHz
-55
2MHz
-60
1MHz
-65
0
1
2
3
4
5
Output Amplitude (Vpp)
DS012790-36
DS012790-35
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10
3rd Harmonic Distortion, RL = 25Ω
CLC452
± 5V Typical Performance Characteristics
(Continued)
2nd Harmonic Distortion, RL = 100Ω
-30
Distortion (dBc)
-40
10MHz
-50
5MHz
-60
1MHz
-70
2MHz
-80
-90
0
1
2
3
4
5
Output Amplitude (Vpp)
DS012790-37
DS012790-38
3rd Harmonic Distortion, RL = 100Ω
2nd Harmonic Distortion, RL = 1kΩ
-50
Distortion (dBc)
-55
10MHz
-60
5MHz
-65
-70
2MHz
-75
1MHz
-80
0
1
2
3
4
5
Output Amplitude (Vpp)
DS012790-39
DS012790-40
3rd Harmonic Distortion, RL = 1kΩ
Recommended RS vs. CL
DS012790-41
DS012790-42
11
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Maximum Output Voltage vs. RL
(Continued)
Differential Gain & Phase
DS012790-44
DS012790-43
IBN, VOS vs. Temperature
Short Term Settling Time
1.5
12
1
8
0.5
4
IBN
IBN (µA)
Offset Voltage Vos (mV)
CLC452
± 5V Typical Performance Characteristics
Vos
0
0
-0.5
-4
-100
-50
0
50
100
150
Temperature (ϒC)
DS012790-45
DS012790-46
Long Term Settling Time
DS012790-47
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12
CLC452 Operation
The CLC452 is a current feedback amplifier built in an
advanced complementary bipolar process. The CLC452
operates from a single 5V supply or dual ± 5V supplies.
Operating from a single supply, the CLC452 has the
following features:
•
Provides 100mA of output current while consuming
15mW of power
•
•
Offers low −78/−85dB 2nd and 3rd harmonic distortion
• Decreases loop gain
• Decreases loop bandwidth
• Reduces gain peaking
• Lowers pulse response overshoot
• Affects frequency response phase linearity
Refer to the Feedback Resistor Selection section for more
details on selecting a feedback resistor value.
Design Information
Single Supply Operation (VCC =+5V, VEE = GND)
The specifications given in the +5V Electrical Characteristics table for single supply operation are measured with a
common mode voltage (VCM) of 2.5V. VCM is the voltage
around which the inputs are applied and the output voltage
are specified.
Operating a single +5V supply, The Common Mode Input
Range (CMIR) of the CLC452 is typically +0.8V to +4.2V.
The typical output range with RL =100Ω is +1.0V to +4.0V.
Provides BW > 80MHz and 1MHz distortion < −70dBc at
VO =2.0VPP
The CLC452 performance is further enhanced in ± 5V supply
application as indicated in the ± 5V Electrical Characteristics table and ± 5V Typical Performance plots.
Current Feedback Amplifiers
Some of the key features of current feedback technology
are:
• Interdependence of AC bandwidth and voltage gain
• Inherently stable at unity gain
• Adjustable frequency response with feedback resistor
• High slew rate
• Fast settling
Current feedback operation can be described using a simple
equation. The voltage gain for a non-inverting or inverting
current feedback amplifier is approximated by Equation 1.
Vo
=
Vin
Av
Rf
1+
Z(jω )
where:
•
•
•
•
AV is the closed loop DC voltage gain
Rf is the feedback resistor
Z(jω) is the CLC450’s open loop transimpedance gain
is the loop gain
DS012790-50
FIGURE 1. Non-Inverting Configuration
For single supply DC coupled operation, keep input signal
levels above 0.8V DC. For input signals that drop below 0.8V
DC, AC coupling and level shifting the signal are
recommended. The non-inverting and inverting configurations for both input conditions are illustrated in the following
2 sections.
DC Coupled Single Supply Operation
Figure 1 and Figure 2 show the recommended non-inverting
and inverting configurations for input signals that remain
above 0.8V DC.
13
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CLC452
The denominator of Equation 1 is approximately equal to 1 at
low frequencies. Near the −3dB corner frequency, the
interaction between Rf and Z(jω) dominates the circuit
performance. The value of the feedback resistor has a large
affect on the circuits performance. Increasing Rf has the
following affects:
Application Division
CLC452
Application Division
(Continued)
DS012790-53
DS012790-51
FIGURE 2. Inverting Configuration
FIGURE 4. AC Coupled Inverting Configuration
AC Coupled Single Supply Operation
Figure 3 and Figure 4 show possible non-inverting and
inverting configurations for input signals that go below 0.8V
DC. The input is AC coupled to prevent the need for level
shifting the input signal at the source. The resistive voltage
divider biases the non-inverting input to VCC ÷ 2 = 2.5V (For
VCC = +5V).
Dual Supply Operation
The CLC452 operates on dual supplies as well as single
supplies. The non-inverting and inverting configurations are
shown in Figure 5 and Figure 6.
DS012790-54
FIGURE 5. Dual Supply Non-Inverting Configuration
DS012790-52
FIGURE 3. AC Coupled Non-Inverting Configuration
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14
resistor at the input or output of the amplifier. Figure 7 shows
typical inverting and non-inverting circuit configurations for
matching transmission lines.
(Continued)
DS012790-56
FIGURE 7. Transmission Line Matching
Non-inverting gain application:
•
•
•
Make R1,R2, R6, R7 equal to Zo.
Use R3 to isolate the amplifier from reactive loading
caused by the transmission line, or by parasitics.
Inverting gain application:
DS012790-55
FIGURE 6. Dual Supply Inverting Configuration
• Connect R3 directly to ground.
• Make the resistors R4, R6, and R7 equal to Zo
• Make R5\ Rg =Zo
The input and output matching resistors attenuate the signal
by a factor of 2, therefore additional gain is needed. Use C6
to match the output transmission line over a greater
frequency range. C6 compensates for the increase of the
amplifier’s output impedance with frequency.
Power Dissipation
Follow these steps to determine the power consumption of
the CLC452:
1. Calculate the quiescent (no-load) power:
Pamp = ICC (VCC − VEE)
2. Calculate the RMS power at the output stage:
Po =(VCC − Vload)(Iload), where Vload and Iload are the
RMS voltage and current across the external load.
3. Calculate the total RMS power: Pt = Pamp + Po
The maximum power that the DIP, SOIC, and SOT packages
can dissipate at a given temperature is illustrated in Figure 8.
The power derating cure for any CLC452 package can be
derived by utilizing the following equation:
Feedback Resistor Selection
The feedback resistor, Rf, affects the loop gain and
frequency response of a current feedback amplifier.
Optimum performance of the CLC452, at a gain of +2V/V, is
achieved with Rf equal to 1kΩ. The frequency response plots
in the Typical Performance sections illustrate the
recommended Rf provide the maximum bandwidth with
minimal peaking. Within limits, Rf can be adjusted to
optimize the frequency response.
•
Connect Rg directly to ground.
Decrease Rf to peak frequency response and extend
bandwidth
•
Increases Rf to roll off frequency response and compress
bandwidth
As a rule of thumb, if the recommended Rf is doubled, then
the bandwidth will be cut in half.
Unity Gain Operation
The recommended Rf for unity gain (+1V/V) operation is
1kΩ. Rg is left open. Parasitic capacitance at the inverting
node may require a slight increase in Rf to maintain a flat
frequency response.
Bandwidth vs. Output Amplitude
The bandwidth of the CLC452 is at a maximum for output
voltages near 1Vpp. The bandwidth decreases for smaller
and larger output amplitudes. Refer to the Frequency
Response vs. Vo plots.
Load Termination
The CLC452 can source and sink near equal amounts of
current. For optimum performance, the load should be tied to
Vcm.
Driving Cables and Capacitive Loads
When driving cables, double termination is used to prevent
reflections. For capacitive load application, a small series
resistor at the output of the CLC452 will improve stability and
settling performance. The Frequency Response vs. CL and
Recommended Rsvs. CL plots, in the typical performance
section, give the recommended series resistance value for
optimum flatness at various capacitive loads.
Transmission Line Matching
One method for matching the characteristic impedance (Zo)
of a transmission line or cable is to place the appropriate
Where
•
15
Tamb = Ambient temperature (˚C)
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CLC452
Application Division
CLC452
Application Division
•
Components Needed to Evaluate the CLC452 on the
Evaluation Board:
• Rf, Rg — Use this product data sheet to select values.
(Continued)
θJA = Thermal resistance, from junction to ambient, for a
given package (˚C/W)
DS012790-58
Layout Considerations
A proper printed circuit layout is essential for achieving high
frequency performance. National provides evaluation boards
for the CLC452 (730013-DIP, 730027-SOIC, 730068-SOT)
and suggests their use as a guide for high frequency layout
and as an aid for device testing and characterization.
General layout and supply bypassing play major roles in high
frequency layout and as an aid for device testing and
characterization.
General layout and supply bypassing play major roles in high
frequency performance. Follow The steps below as a bias
for high frequency layout:
Include 6.8µF tantalum and 0.1µF ceramic capacitors on
both supplies
•
Place the 6.8µF capacitors within 0.75 inches of the
power pins.
•
Place the 0.1µF capacitors less than 0.1 inches from the
power pins
•
Remove the ground plane under and around the part,
especially near the input and output pins to reduce
parasitic capacitance.
•
•
Minimize all trace lengths to reduce series inductances.
Rin, Rout - Typically 50Ω (Refer to the Basic Operation
section of the evaluation board data sheet for details)
•
Rf — Optional resistor for inverting gain configurations
(Select Rf to yield desired input impedance = Rg\Rf
• C1, C2-0.1µF ceramic capacitors
• C3, C4-6.8µF tantalum capacitors
Components not used:
• C5, C6, C7, C8
• R1 thru R8
The evaluation boards are designed to accommodate dual
supplies. The boards can be modified to provide single
supply operation. For best performance; 1) do not connect
the unused supply, 2) ground the unused supply pin.
SPICE Models
SPICE models provide a means to evaluate amplifier
designs. Free SPICE modes are available for National’s
monolithic amplifiers that:
• Support Berkeley SPICE 2G and its many derivatives
• Reproduce typical DC, AC, Transient, and Noise
performance
• Support room temperature simulations
The readme file that accompanies the diskette lists released
models, and provides a list of modeled parameters. The
application note OA-18, Simulation SPICE Models for
National’s Op Amps, contains schematics and a
reproduction of the readme file.
Application Circuits
Single Supply Cable Driver
The typical application shown on the front page shows the
CLC452 driving 10m of 75Ω coaxial cable. The CLC452 is
set for a gain of +2V/V to compensate for the divide-by-two
voltage drop at Vo.
Single Supply Lowpass Filter
Figure 9 and Figure 10 illustrate a lowpass filter and design
equation. The circuit operates from a single supply of +5V.
The voltage divider biases the non-inverting input to 2.5V.
And the input is AC coupled to prevent the need for level
shifting the input signal at the source. Use the design
equations to determine R1, R2, C1 and C2 based on the
desired Q and corner frequency.
FIGURE 8. Power Derating Curves
•
•
Use flush-mount printed circuit board pins for prototyping,
never use high profile DIP sockets.
•
Evaluation Board Information
Data sheet are available for the CLC730013/CLC730027
and CLC730068 evaluation boards. The velitation board
data sheets provide:
• Evaluation board schematics
• Evaluation board layouts
• General information about the boards
The CLC730013/CLC730027 data sheet also contains
tables of recommended components to evaluate several of
National’s high speed amplifiers. This table for the CLC452
is illustrated below. Refer to the evaluation board data sheet
for schematics and further information.
www.national.com
DS012790-59
FIGURE 9. Lowpass Filter Topology
16
CLC452
Application Division
(Continued)
DS012790-61
FIGURE 11. Lowpass Response
Twisted Pair Driver
The high output current and low distortion, of the CLC452,
make it well suited for driving transformers. Figure 12
illustrates a typical twisted pair driver utilizing the CLC452
and a transformer. The transformer provides the signal and
its inversion for the twisted pair.
DS012790-60
FIGURE 10. Design Equations
This example illustrates a lowpass filter with Q = 0.707 and
corner frequency fc = 10MHz. AQ of 0.707 was chosen to
achieve a maximally flat, Butterworth response. Figure 11
indicates the filter response.
DS012790-62
FIGURE 12. Twisted Pair Driver
To match the line’s characteristic impedance (Zo) set:
• RL = ZO
• Rm = Req
Where Req is the transformed value of the load impedance,
(RL), and is approximated by:
Req = RL/n2
Select the transformer so that it loads the line with a value
close to Zo, over the desired frequency range. The output
impedance, Ro, of the CLC452 varies within frequency and
can also affect the return loss. The return loss, shown below,
takes into account an ideal transformer and the value of Ro
The load current (Ii) and voltage (VO) are related to the
CLC452’s maximum output voltage and current by:
From the above current relationship, it is obvious that an
amplifier with high output drive capability is required.
17
www.national.com
CLC452
Physical Dimensions
inches (millimeters) unless otherwise noted
8-Pin SOIC
NS Package Number M08A
5-Pin SOT23
NS Package Number MA05A
www.national.com
18
inches (millimeters) unless otherwise noted (Continued)
8-Pin MDIP
NS Package Number N08E
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DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
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2. A critical component is any component of a life
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the life support device or system, or to affect its
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Email: ap.support@nsc.com
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National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
CLC452 Single Supply, Low Power, High Output, Current Feedback Amplifier
Physical Dimensions
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