CLC450 Single Supply, Low Power, High Output, Current Feedback Amplifier General Description The CLC450 has a new output stage that delivers high output drive current (100mA), but consumes minimal quiescent supply current (1.5mA) 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 CLC450 offers superior dynamic performance with a 100MHz small signal bandwidth, 280V/µs slew rate and 6.1ns rise/fall times (2VSTEP). The combination of low quiescent power, high output current drive, and high speed performance make the CLC450 well suited for many battery powered personal communication/computing systems. The ability to drive low impedance, highly capacitive loads, makes the CLC450 ideal for single ended cable applications. It also drives low impedance loads with minimum distortion. The CLC450 will drive a 100Ω load with only −75/−64dBc second/third harmonic distortion (AV =+2, VOUT = 2VPP, f = 1MHz). With a 25Ω load, and the same conditions, it produces only −70/−60dBc 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 CLC450 provides excellent −79/−75dBc second/third harmonic distortion (AV = +2, VOUT = 2VPP, f = 1MHz, RL = 1kΩ) and fast settling time. Available in SOT23-5, the CLC450 is ideal for applications where space is critical. n n n n n n −79/−75dBc HD2/HD3 (1MHz) 20ns settling to 0.05% 280V/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 1.5mA supply current n 100MHz bandwidth (AV = +2) DS012733-65 Connection Diagrams DS012733-3 DS012733-4 Pinout DIP & SOIC © 2001 National Semiconductor Corporation DS012733 Pinout SOT23-5 www.national.com CLC450 Single Supply, Low Power, High Output, Current Feedback Amplifier March 2001 CLC450 Typical Application DS012733-1 Single Supply Cable Driver DS012733-2 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 CLC450AJP CLC450AJP N08E 8-pin plastic SOIC −40˚C to +85˚C CLC450AJE CLC450AJE M08A 5-pin SOT −40˚C to +85˚C CLC450AJM5 A20 MA05A www.national.com 2 ESD Rating (human body model) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/Distributors for availability and specifications. Operating Ratings Supply Voltage (VCC - VEE) Output Current (see note 3) Common Mode Input Voltage Maximum Junction Temperature Storage Temperature Range Lead Solder Duration (+300˚C) Thermal Resistance Package MDIP SOIC SOT23 +14V 140mA VEE to VCC +150˚C −65˚C to +150˚C 10 sec 500V (θJC) 115˚C/W 130˚C/W 140˚C/W (θJA) 125˚C/W 150˚C/W 210˚C/W +5V Electrical Characteristics AV = +2, Rf = 1k, RL = 100Ω, VS = +5 (Note 4), VCM = VEE + (VS/2), RL tied to VCM; unless specified Symbol Parameter Ambient Temperature Conditions CLC450AJ Typ Min/Max (Note 2) Units +25˚C +25˚C 0 to 70˚C −40 to 85˚C VO < 0.5VPP 100 85 75 70 MHz VO < 2.0VPP 75 60 55 50 MHz −0.1dB Bandwidth VO < 0.5VPP 30 25 20 20 MHz Gain Ppeaking < 200MHz, VO < 0.5VPP < 30MHz, VO < 0.5VPP < 30MHz, VO = 0.5VPP 0 0.5 0.9 1.0 dB 0.1 0.3 0.4 0.5 dB 0.2 0.4 0.5 0.5 deg Rise and Fall Time 2V Step 6.1 8.5 9.2 10.0 ns Settling Time to 0.05% 1V Step 20 30 50 80 ns Overshoot 2V Step 16 20 22 22 % Slew Rate 2V Step 280 200 185 170 V/µs Frequency Domain Response -3dB Bandwidth Gain Rolloff Linear Phase Deviation TIME DOMAIN RESPONSE DISTORTION AND NOISE RESPONSE 2nd Harmonic Distortion 3rd Harmonic Distortion 2VPP,1MHz −75 - - - dBc 2VPP, 1MHz, RL = 1kΩ −79 - - - dBc 2VPP, 5MHz −62 -58 -57 -56 dBc 2VPP, 1MHz −64 - - - dBc 2VPP, 1MHz, RL = 1kΩ −75 - - - dBc 2VPP, 5MHz −52 -48 -46 -46 dBc Voltage (eni) > 1MHz 3.0 3.7 4.0 4.0 nV/ Non-Inverting Current (ibn) > 1MHz 6.9 9 10 10 pA/ Inverting Current (ibi) > 1MHz 8.5 11 12 12 pA/ 1 4 5 6 mV 7 - 15 15 µV/˚C 5 12 15 16 µA Equivalent Input Noise Static, DC Performance Input Offset Voltage (Note 5) Average Drift Input Bias Current (Non-Inverting) (Note 5) Average Drift Input Bias Current (Inverting) (Note 5) Average Drift 25 - 60 60 nA/˚C 3 10 12 13 µA 10 - 20 20 nA/˚C Power Supply Rejection Ratio DC 54 50 48 48 dB Common Mode Rejection Ratio DC 51 47 45 45 dB 3 www.national.com CLC450 Absolute Maximum Ratings (Note 1) CLC450 +5V Electrical Characteristics (Continued) AV = +2, Rf = 1k, RL = 100Ω, VS = +5 (Note 4), VCM = VEE + (VS/2), RL tied to VCM; unless specified Symbol Parameter Conditions Typ Min/Max (Note 2) Units Static, DC Performance Supply Current (Note 5) RL = ∞ 1.5 1.7 1.8 1.8 mA Input Resistance (Non-Inverting) 0.46 0.37 0.33 0.33 MΩ Input Capacitance (Non-Inverting) 1.5 2.3 2.3 2.3 pF Input Voltage Range, High 4.2 4.1 4.1 4.0 V Input Voltage Range, Low 0.8 0.9 0.9 1.0 V Miscellaneous Performance Output Voltage Range, High RL = 100Ω 4.0 3.9 3.9 3.8 V Output Voltage Range, Low RL = 100Ω 1.0 1.1 1.1 1.2 V Output Voltage Range, High RL = ∞ 4.1 4.0 4.0 3.9 V Output Coltage Range, Low RL = ∞ 0.9 1.0 1.0 1.1 V 100 80 65 40 mA 55 90 90 120 mΩ Output Current (Note 3) Output Resistance, Closed Loop DC ± 5V Electrical Characteristics AV = +2, VCC = ± 5V, RL = 100Ω, Rf = 1kΩ; unless specified Symbol Parameterm Ambient Temperature Conditions CLC450AJ Typ Min/Max (Note 2) Units +25˚C +25˚C 0 to 70˚C −40 to 85˚C VO < 1.0VPP 135 115 105 100 MHz VO < 4.0VPP 55 45 42 40 MHz 40 30 25 25 MHz 0 0.5 0.9 1.0 dB 0.1 0.3 0.4 0.5 dB Linear Phase Deviation VO < 1.0VPP < 200MHz, VO < 1.0VPP < 30MHz, VO < 1.0VPP < 30MHz, VO < 1.0VPP) 0.1 0.3 0.4 0.4 deg Differential Gain NTSC, RL = 150Ω 0.03 - - - % Differential Phase NTSC, RL = 150Ω 0.3 - - - deg Rise and Fall Time 2V Step 4.4 5.8 6.2 6.8 ns Settling Time to ± 0.05% 2V Step 15 25 40 60 ns Overshoot 2V Step 15 20 22 22 % Slew Rate 2V Step 370 280 260 240 V/µs Frequency Domain Response -3dB Bandwidth −0.1dB Bandwidth Gain Peaking Gain Rolloff TIME DOMAIN RESPONSE DISTORTION AND NOISE RESPONSE 2nd Harmonic Distortion 2VPP, 1MHz −86 - - - dBc 2VPP, 1MHz, RL = 1kΩ −85 - - - dBc 2VPP, 5MHz −68 −64 −61 −60 dBc 2VPP, 1MHz −65 - - - dBc 2VPP, 1MHz, RL = 1kΩ −74 - - - dBc 2VPP, 5MHz −52 −48 −46 −46 dBc Voltage (eni) > 1MHz 3.0 3.7 4.0 4.0 nV/ Non-Inverting Current (ibn) > 1MHz 6.9 9 10 10 pA/ Inverting Current (ibi) > 1MHz 8.5 11 12 12 pA/ 3rd Harmonic Distortion Equivalent Input Noise www.national.com 4 CLC450 ± 5V Electrical Characteristics (Continued) AV = +2, VCC = ± 5V, RL = 100Ω, Rf = 1kΩ; unless specified Symbol Parameterm Conditions Typ Min/Max (Note 2) Units Static, DC Performance Input Offset Voltage 2 Average Drift Input Bias Current (Non-Inverting) Average Drift Input Bias Current (Inverting) Average Drift 6 7 8 mV 8 - 20 20 µV/˚C 5 12 16 17 µA 40 - 70 70 nA/˚C 5 13 15 16 µA 20 - 45 45 nA/˚C Power Supply Rejection Ratio DC 56 51 49 49 dB Common-Mode Rejection Ratio DC 53 48 46 46 dB Supply Current RL = ∞ 1.6 1.9 2.0 2.0 mA 0.62 0.50 0.45 0.45 MΩ Miscellaneous Performance Input Resistance (Non-Inverting) Input Capacitance (Non-Inverting) Common-Mode Input Range Output Voltage Range RL = 100Ω Output Voltage Range RL = ∞ Output Current (Note 3) Output Resistance, Closed Loop DC 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 40 70 70 90 mΩ 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: VS = VCC −VEE Note 5: AJ-level: spec. is 100% tested at +25˚C. +5V Typical Performance Characteristics Non-Inverting Frequency Response Inverting Frequency Response DS012733-5 DS012733-6 5 www.national.com Frequency Response vs. RL (Continued) Frequency Response vs. VO DS012733-7 Frequency Response vs. CL DS012733-8 Open Loop Transimpedance Gain, Z(s) DS012733-9 Gain Flatness DS012733-10 Equivalent Input Noise Magnitude (0.05dB/div) CLC450 +5V Typical Performance Characteristics 10 20 30 Frequency (MHz) DS012733-11 DS012733-12 www.national.com 6 2nd & 3rd Harmonic Distortion CLC450 +5V Typical Performance Characteristics (Continued) 2nd Harmonic Distortion, RL = 25Ω DS012733-14 DS012733-13 3rd Harmonic Distortion, RL = 25Ω 2nd Harmonic Distortion, RL = 100Ω DS012733-15 3rd Harmonic Distortion, RL = 100Ω DS012733-16 2nd Harmonic Distortion, RL = 1kΩ Distortion (dBc) -30 -40 10MHz -50 5MHz -60 2MHz 1MHz -70 0 0.5 1 1.5 2 2.5 Output Amplitude (Vpp) DS012733-17 DS012733-18 7 www.national.com CLC450 +5V Typical Performance Characteristics 3rd Harmonic Distortion, RL = 1kΩ (Continued) Closed Loop Output Resistance DS012733-20 DS012733-19 Recommended RS vs. CL Large & Small Signal Pulse Response DS012733-22 DS012733-21 PSRR & CMRR IBI, IBN, VOS vs. Temperature DS012733-24 DS012733-23 www.national.com 8 CLC450 +5V Typical Performance Characteristics (Continued) Maximum Output Voltage vs. RL DS012733-25 ± 5V Typical Performance Characteristics Non-Inverting Frequency Response Inverting Frequency Response DS012733-26 Frequency Response vs. RL DS012733-27 Frequency Response vs. VO DS012733-28 DS012733-29 9 www.national.com Frequency Response vs. CL (Continued) Gain Flatness Magnitude (0.05dB/div) CLC450 ± 5V Typical Performance Characteristics 10 20 30 Frequency (MHz) DS012733-31 DS012733-30 Small Signal Pulse Response Large Signal Pulse Response DS012733-32 2nd & 3rd Harmonic Distortion DS012733-33 2nd Harmonic Distortion, RL = 25Ω DS012733-35 DS012733-34 www.national.com 10 3rd Harmonic Distortion, RL = 25Ω CLC450 ± 5V Typical Performance Characteristics (Continued) 2nd Harmonic Distortion, RL = 100Ω DS012733-36 3rd Harmonic Distortion, RL = 100Ω DS012733-37 2nd Harmonic Distortion, RL = 1kΩ DS012733-38 3rd Harmonic Distortion, RL = 1kΩ DS012733-39 Recommended RS vs. CL DS012733-40 DS012733-41 11 www.national.com Maximum Output Voltage vs. RL (Continued) Differential Gain & Phase DS012733-43 DS012733-42 IBI, IBN, VOS vs. Temperature Short Term Settling Time 1.5 12 1 8 IBI 0.5 4 IBN Vos 0 IBI, IBN (µA) Offset Voltage Vos (mV) CLC450 ± 5V Typical Performance Characteristics 0 -0.5 -4 -100 -50 0 50 100 150 Temperature (ϒC) DS012733-44 DS012733-45 Long Term Settling Time DS012733-46 www.national.com 12 CLC450 Operation The CLC450 is a current feedback amplifier built in an advanced complementary bipolar process. The CLC450 operates from a single 5V supply or dual ± 5V supplies. Operating from a single supply, the CLC450 has the following features: • Provides 100mA of output current while consuming 7.5mW of power • • Offers low −79/−75dB 2nd and 3rd harmonic distortion Provides BW > 60MHz and 1MHz distortion < −65dBc at VO = 2.5VPP The CLC450 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: • Independence of AC bandwidth and voltage gain • Inherently stable at unity gain • Adjustable fequency 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. DS012733-47 Equation 1. 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. (1) where: • AV is the closed loop DC voltage gain • Rf is the feedback resistor • Z(j(ω)) is the CLC450’s open loop transimpedance gain • Z(j(ω))/Rf is the loop gain The denominator of Equation 1 is approximately equal to 1 at low frequencies. Near the -3dB corner frequency, the interaction between Rf and Z(j(ω) dominates the circuit performance. The value of the feedback resistor has a large affect on the circuits performance. Increasing Rf has the following affects: • Decreases loop gain • Decreases 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 voltages are specified. DS012733-50 FIGURE 2. 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). 13 www.national.com CLC450 Operating from a single +5V supply, The Common Mode Input Range (CMIR) of the CLC450 is typically +0.8V to +4.2V. The typical output range with RL = 100Ω is +1.0V to +4.0V. Application Division CLC450 Application Division (Continued) DS012733-53 FIGURE 5. Dual Supply Non-Inverting Configuration DS012733-51 FIGURE 3. AC Coupled Non -Inverting Configuration DS012733-54 FIGURE 6. Dual Supply Inverting Configuration Feedback Resistor Selection The feedback resistor, Rf, affects the loop gain and frequency response of a current feedback amplifier. Optimum performance of the CLC450, 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 for several gains. These recommended values of Rf provide the maximum bandwidth with minimal peaking. Within limits, Rf can be adjusted to optimize the frequency response. DS012733-52 FIGURE 4. AC Coupled Inverting Configuration Dual Supply Operation The CLC450 operates on dual supplies as well as single supplies. The non-inverting and inverting configurations are shown in Figure 5 and Figure 6. • • 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. www.national.com 14 (Continued) 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 Unity Gain Operation The recommended Rf for unity gain (+1V/V) operation is 1.5kΩ. Rg is left open. Parasitic capacitance at the inverting node may require a slight increase in Rf to maintain a flat frequency response. 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 CLC450 package can be derived by utilizing the following equation: Bandwidth vs. Output Amplitude The bandwidth of the CLC450 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 CLC450 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 CLC450 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 resistor at the input or output of the amplifier. Figure 7 shows typical inverting and non-inverting circuit configurations for matching transmission lines. Where • • Tamb = Ambient temperature (˚C) θJA = Thermal resistance, from junction to ambient, for a given package (˚C/W) DS012733-57 FIGURE 8. Power Derating Curves Connect Rg directly to ground. Layout Considerations A proper printed circuit layout is essential for achieving high frequency performance. National provides evaluation boards for the CLC450 (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 performance. Follow the steps below as a basis for high frequency layout: Make R1,R2, R6, R7 equal to Zo. • 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. DS012733-55 FIGURE 7. Transmission Line Matching Non-inverting gain applications: • • • Use R3 to isolate the amplifier from reactive loading caused by the transmission line, or by parasitics. Inverting gain applications: • 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 CLC450: 1. Calculate the quiescent (no-load) power: Pamp = ICC (VCC − VEE) 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 evaluation board data sheets provide: • • 15 Evaluation board schematics Evaluation board layouts www.national.com CLC450 Application Division CLC450 Application Division (Continued) • 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 CLC450 is illustrated below. Refer to the evaluation board data sheet for schematics and further information. Components Needed to Evaluate the CLC450 on the Evaluation Board: • Rf, Rg — Use this product data sheet to select values. • 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- 0.1 µF ceramic capacitors • C3, C4- 6.8 µF tantalum capacitors • C5, C6, C7, C8 • R1 thru R8 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 models 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 CLC450 driving 10m of 75Ω coaxial cable. The CLC450 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 equations. 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. DS012733-58 FIGURE 9. Lowpass Filter Topology Gain = K = 1 + Rf Rg Corner frequency = ω c = 1 R1R2C1C2 1 Q= R 2C 2 + R1C1 R1C1 R1C2 + (1− K) R2C1 R 2C 2 For R1 = R2 = R and C1 = C2 = C ωc = Q= 1 RC 1 (3 − K) DS012733-59 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. DS012733-60 FIGURE 11. Lowpass Response www.national.com 16 Where Req is the transformed value of the load impedance, (RL), and is approximated by: (Continued) Twisted Pair Driver The high output current and low distortion, of the CLC450, make it well suited for driving transformers. Figure 12 illustrates a typical twisted pair driver utilizing the CLC450 and a transformer. The transformer provides the signal and its inversion for the twisted pair. 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 CLC450 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 DS012733-61 FIGURE 12. Twisted Pair Driver The load current (Ii) and voltage (Vo) are related to the CLC450’s maximum output voltage and current by: To match the line’s characteristic impedance (Zo) set: • • RL = ZO Rm = Req From the above current relationship, it is obvious that an amplifier with high output drive capability is required. 17 www.national.com CLC450 Application Division CLC450 Physical Dimensions inches (millimeters) unless otherwise noted 8-Pin SOIC NS Package Number M08A 8-Pin MDIP NS Package Number N08E www.national.com 18 inches (millimeters) unless otherwise noted (Continued) 5-Pin SOT23 NS Package Number MA05A LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT 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 into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: [email protected] www.national.com National Semiconductor Europe Fax: +49 (0) 180-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: [email protected] National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 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. CLC450 Single Supply, Low Power, High Output, Current Feedback Amplifier Physical Dimensions