N CLC440 High-Speed, Low-Power, Voltage Feedback Op Amp General Description Features The CLC440 is a wideband, low-power, voltage feedback op amp that offers 750MHz unity-gain bandwidth, 1500V/µs slew rate, and 90mA output current. For video applications, the CLC440 sets new standards for voltage feedback monolithics by offering the impressive combination of 0.015% differential gain and 0.025° differential phase errors while dissipating a mere 70mW. ■ The CLC440 incorporates the proven properties of Comlinear’s current feedback amplifiers (high bandwidth, fast slewing, etc.) into a “classical” voltage feedback architecture. This amplifier possesses truly differential and fully symmetrical inputs both having a high 900kΩ impedance with matched low input bias currents. Furthermore, since the CLC440 incorporates voltage feedback, a specific Rf is not required for stability. This flexibility in choosing Rf allows for numerous applications in wideband filtering and integration. ■ ■ ■ ■ ■ ■ ■ ■ Applications ■ ■ ■ ■ ■ ■ Unlike several other high-speed voltage feedback op amps, the CLC440 operates with a wide range of dual or single supplies allowing for use in a multitude of applications with limited supply availability. The CLC440’s low 3.5nV/√Hz(en) and 2.5pA/√Hz(in) noise sets a very low noise floor. Typical Application Unity-gain stable High unity-gain bandwidth: 750MHz Ultra-low differential gain: 0.015% Very low differential phase: 0.025° Low power: 70mW Extremely fast slew rate: 1500V/µs High output current: 90mA Low noise: 3.5nV/√Hz Dual ±2.5V to ±6V or single 5V to 12V supplies ■ ■ ■ Professional video Graphics workstations Test equipment Video switching & routing Communications Medical imaging A/D drivers Photo diode transimpedance amplifiers Improved replacement for CLC420 or OPA620 Frequency Response (AV = +2V/V) CLC440 High-Speed, Low-Power, Voltage Feedback Op Amp June 1999 Generator Waveforms 10MHz to 40MHz Square and Triangular Wave Generator Pinout DIP & SOIC © 1999 National Semiconductor Corporation Printed in the U.S.A. http://www.national.com CLC440 Electrical Characteristics (AV = +2, Rf = Rg = 250Ω: Vcc = + 5V, RL = 100Ω unless specified) PARAMETERS Ambient Temperature CONDITIONS CLC440 TYP +25˚C FREQUENCY DOMAIN RESPONSE -3dB bandwidth AV =+2 Vout < 0.2Vpp Vout < 4.0Vpp -3dB bandwidth AV =+1 Vout < 0.2Vpp gain bandwidth product Vout < 0.2Vpp gain flatness Vout < 2.0Vpp DC to 75MHz linear phase deviation Vout < 2.0Vpp DC to 75MHz differential gain 4.43MHz, RL=150Ω differential phase 4.43MHz, RL=150Ω TIME DOMAIN RESPONSE rise and fall time 2V step 4V step 2V step 4V step 4V step, ±0.5V crossing settling time to 0.05% overshoot slew rate DISTORTION AND NOISE RESPONSE 2nd harmonic distortion 2Vpp, 5MHz 2Vpp, 20MHz 3rd harmonic distortion 2Vpp, 5MHz 2Vpp, 20MHz equivalent input noise voltage >1MHz current >1MHz STATIC DC PERFORMANCE input offset voltage average drift input bias current average drift input offset current average drift power supply rejection ratio common-mode rejection ratio supply current DC DC RL= ∞ MISCELLANEOUS PERFORMANCE input resistance common-mode input capacitance common-mode differential-mode input voltage range common-mode output voltage range RL= 100Ω output voltage range RL= ∞ output current MIN/MAX RATINGS +25˚C 0 to 70˚C -40 to 85˚C UNITS 260 190 750 230 0.05 0.8 0.015 0.025 165 150 165 135 135 130 0.15 1.2 0.03 0.05 0.20 1.5 0.04 0.06 0.20 1.5 0.04 0.06 MHz MHz MHz MHz dB deg % deg 1.5 3.2 10 7 1500 2.0 4.2 14 13 900 2.2 4.5 16 13 750 2.5 5.0 16 13 600 ns ns ns % V/µs -64 -52 -70 -51 -59 -46 -65 -45 -59 -46 -64 -43 -59 -46 -64 -43 dBc dBc dBc dBc 3.5 2.5 4.5 3.5 5.0 4.0 5.0 4.0 nV/√Hz pA/√Hz 4.0 10 40 60 3.0 10 58 60 8.0 mV µV/°C µA nA/°C µA nA/°C dB dB mA 300 2.0 1.0 ±2.7 ±2.2 ±2.7 ±45 kΩ pF pF V V V mA 1.0 5.0 10 30 0.5 3.0 65 80 7.0 3.0 2.0 58 65 7.5 3.5 10 35 50 2.0 10 58 60 8.0 900 1.2 0.5 ±3.0 ±2.5 ±3.0 ±80 500 2.0 1.0 ±2.8 ±2.3 ±2.8 ±72 400 2.0 1.0 ±2.7 ±2.2 ±2.7 ±65 30 NOTES A A A A Min/max ratings are based on product characterization and simulation. Individual parameters are tested as noted. Outgoing quality levels are determined from tested parameters. Absolute Maximum Ratings voltage supply Iout is short circuit protected to ground common-mode input voltage maximum junction temperature storage temperature range lead temperature (soldering 10 sec) ESD rating (human bodey model) Ordering Information ±6V Model CLC440AJP CLC440AJE CLC440A8B ±Vcc +150˚C -65˚C to +150˚C +300˚C <1000V Plastic (AJP) Surface Mount (AJE) CerDip http://www.national.com θjc θja 70˚/W 60˚/W 40˚/W 125˚/W 140˚/W 130˚/W -40˚C to +85˚C -40˚C to +85˚C -55˚C to +125˚C Description 8-pin PDIP 8-pin SOIC 8-pin hermetic CerDIP, MIL-STD-883 Contact factory for SMD number. Notes Package Thermal Resistance Package Temperature Range A) J-level: spec is 100% tested at +25˚C. Transitor Count 2 46 CLC440 Typical Performance Characteristics (AV = +2, Rf = 250Ω:Vcc = + 5V, RL = 100Ω unless specified) Non-Inverting Frequency Response Inverting Frequency Response AV = 1(Rf = 0) AV = -1 RL=1K AV = 2 0 AV = 1 -45 AV = 10 -90 AV = 5 -135 AV = -5 AV -1 Phase -180 -225 AV -10 AV -5 -270 AV -2 -315 -180 10 100 1 1000 10 100 10 Magnitude (1dB/div) -45 Vout = 5Vpp -90 -135 Vout = 200mVpp CL = 100pF Rs = 30 CL = 1000pF Rs = 5 CL = 10pF CL = 100pF Phase 0 CL = 1000pF + -45 -90 Rs -135 1k CL - -180 100 1000 Gain Phase (1.0deg/div) 0 100 Gain Flatness and Linear Phase Phase (deg) Vout = 2Vpp -135 Frequency (MHz) CL = 10pF Rs = 50 Gain Vout = 2Vpp Phase (deg) Magnitude (1dB/div) -90 1 1000 Vout = 200mVpp Gain 10 -45 -180 Frequency Response vs. Capacitive Load Vout = 5Vpp 0 RL=50 Frequency (MHz) Frequency Response vs. Vout 1 RL=1K Phase -360 Frequency (MHz) Phase RL=50 RL=100 Magnitude (0.05dB/div) 1 RL=100 Phase (deg) AV = 2 Phase AV = -2 AV = -10 (Rf = 500Ω) Phase (deg) Phase (deg) AV = 5 AV = 10 Gain Magnitude (1dB/div) Gain Magnitude (1dB/div) Gain Magnitude (1dB/div) Frequency Response vs. Load Phase -180 1 1000 10 Frequency (MHz) 100 0 1000 75 Frequency (MHz) Open Loop Gain and Phase Frequency (7.5MHz/div) BW vs. Gain for Transimpedance Configuration 80 0 Equivalent Input Noise 400 10 10 Cf 4 320 Phase Cf (pF) 0 40 8 -90 0 -180 16 -270 100M 20 10k 1k 100k 1M 10M Cf BW 1.6 123 240 160 12 80 Cd = 20pF BW 100 0 10000 1000 Frequency (Hz) Voltage = 3.5nV/√Hz Current = 2.5pA/√Hz 1 100M 1 100 1k 10k Rf Harmonic Distortion vs. Frequency -45 Rf 1000 See dashed lines 20 -20 Cd = 5pF Bandwidth (MHz) Example Phase (deg) Open Loop Gain (dB) 60 Noise Current (pA/√Hz) Cd = 1pF Noise Voltage (nV/√Hz) Gain 100k 1M 10M Frequency (Hz) PSRR, CMRR, and Closed Loop Rout 1dB Compression 45 Vo = 2Vpp 100 5MHz CMRR -75 2nd RL = 100 3rd RL = 100 -85 PSRR/CMRR (dB) Gain (1dB/div) -65 20MHz 50MHz + 2nd RL = 1k 100MHz 50Ω - 250Ω 3rd RL = 1k Pout 50Ω 35 80 PSRR 25 60 15 40 5 20 Rout 250Ω -95 0 0.1 1 50 10 -4 16 10k 10M 100M Frequency (Hz) Differential Gain and Phase Intercept Point (+dBm) Output Output 1.4 Input 1.0 30 20 + 50Ω - 10 250Ω Pout 120 160 Frequency (20MHz/div) 200 1 0.04 Phase Negative Sync 50Ω 250Ω 80 0.08 Gain Negative Sync Gain Positive Sync 0 40 0.12 Phase Positive Sync 40 10 Frequency (MHz) 3 100 1 0 2 3 Differential Gain (%), Phase (deg) 50Ω 50Ω 0 1M 100k Output Power (Pout) - 250Ω 1.8 12 50 + 50Ω 8 2-Tone, 3rd Order Intermodulation Intercept Input 2.2 4 0 Frequency (MHz) Input and Output VSWR VSWR Rout (Ω) Distortion (dBc) -55 4 Number of 150Ω Loads http://www.national.com CLC440 Typical Performance Characteristics (AV = +2, Rf = 250Ω:Vcc = + 5V, RL = 100Ω unless specified) Input Offset Voltage, Vio (mV) Output Voltage (0.5V/div) 0 -1.0 AV = -2 -2.0 2 0 los -2 -0.4 lb -0.8 -6 Vio -10 -1.2 -1.6 Time (5ns/div) -14 -60 20 -20 60 100 0.05% Settling Time vs. Capacitive Load 80 55 Rs 60 45 + 40 25 Ts 0 10 140 -0.1 -0.2 Ib and Ios vs. Common-Mode Voltage 0.2 Offset Current, Ios (5nA/div) Settling Error % of Output Step 0 15 1000 100 Load Capacitance CL (pF) Long Term Settling Time 0.1 35 1k 0.1 0 -0.1 20 2.0 10 1.0 Ib 0 0 los -10 -1.0 -20 -2.0 Bias Current, Ib (0.5µA/div) Settling Error % of Output Step Short Term Settling Time CL 20 Temperature (C°) 0.2 Rs - Recommended Rs (Ω) AV = +2 1.0 6 Settling Time, Ts(ns) to 0.05% Typical DC Errors vs. Temperature 0.4 Input Bias, Offset Current, lb los (µA) Pulse Response 2.0 -0.2 0 20 40 60 10-9 10-8 10-7 10-6 100 80 Time (ns) 10-5 10-4 10-3 10-2 10-1 100 -4.0 Time (s) -2.4 -0.8 0.8 2.4 4.0 Common-Mode Input Voltage (V) APPLICATION INFORMATION General Design Equations The CLC440 is a unity gain stable voltage feedback amplifier. The matched input bias currents track well over temperature. This allows the DC offset to be minimized by matching the impedance seen by both inputs. Output Drive and Settling Time Performance The CLC440 has large output current capability. The 90mA of output current makes the CLC440 an excellent choice for applications such as: • Video Line Drivers • Distribution Amplifiers Gain The non-inverting and inverting gain equations for the CLC440 are as follows: Non-inverting Gain: 1 + Inverting Gain: − When driving a capacitive load or coaxial cable, include a series resistance Rs to back match or improve settling time. Refer to the “Settling Time vs. Capacitive Load” plot in the typical performance section to determine the recommended resistance for various capacitive loads. Rf Rg Rf Rg When driving resistive loads of under 500Ω, settling time performance diminishes. This degradation occurs because a small change in voltage on the output causes a large change of current in the power supplies. This current creates ringing on the power supplies. A small resistor will dampen this effect if placed in series with the 6.8µF bypass capacitor. Gain Bandwidth Product The CLC440 is a voltage feedback amplifier, whose closed-loop bandwidth is approximately equal to the gain-bandwidth product (GBP) divided by the gain (Av). For gains greater than 5, Av sets the closed-loop bandwidth of the CLC440. Closed Loop Bandwidth = Av = (Rf + Rg ) Noise Figure Noise Figure (NF) is a measure of noise degradation caused by an amplifier. GBP Av e 2 S /N NF = 10LOG i i = 10LOG ni2 So /No et where, Rg GBP = 230MHz eni = Total Equivalent Input Noise Density Due to the Amplifier et = Thermal Voltage Noise ( 4kTR seq) For gains less than 5, refer to the frequency response plots to determine maximum bandwidth. http://www.national.com 4 Figure 1 shows the noise model for the non-inverting amplifier configuration. The model includes all of the following noise sources: Noise Figure vs. Source Resistance 25 Noise Figure (dB) Rs(Ω) NF Unterminated NF Terminated • Input voltage noise (en) • Input current noise (in = in+ = in-) • Thermal Voltage Noise (et) associated with each external resistor en 4kTRseq * 15 - 10 Ropt = 1400Ω 100 4kTRf Rg 1k 10k 100k Source Resistance (Ω) * * 6.15dB Ropt = 2800Ω 10 Rf in- 17.90dB 3.13dB Unterminated 0 * * 12.03dB Terminated CLC440 in+ 50 ROPT 5 + * Rseq 20 Figure 2: Noise Figure vs. Source Resistance These boards were laid out for optimum, high-speed performance. The ground plane was removed near the input and output pins to reduce parasitic capacitance. And all trace lengths were minimized to reduce series inductances. 4kTRg Rseq = Rs for Unterminated Systems Rseq = Rs II RT for Terminated Systems Figure 1: Non-inverting Amplifier Noise Model Supply bypassing is required for the amplifiers performance. The bypass capacitors provide a low impedance return current path at the supply pins. They also provide high frequency filtering on the power supply traces. 6.8µF tantalum, 0.01µF ceramic, and 500pF ceramic capacitors are recommended on both supplies. Place the 6.8µF capacitors within 0.75 inches of the power pins, and the 0.01µF and 500pF capacitors less than 0.1 inches from the power pins. The total equivalent input noise density is calculated by using the noise model shown. Equations 1 and 2 represent the noise equation and the resulting equation for noise figure. ( ) ( ) ( ) 2 eni = en2 + in2 R seq2 + R fIIRg + 4kTRseq + 4kT R fIIRg Equation 1: Noise Equation ( ) 2 2 e + in2 R seq2 + R fIIRg + 4kTRseq + 4kT R fIIRg n NF = 10LOG 4kTR seq Dip sockets add parasitic capacitance and inductance which can cause peaking in the frequency response and overshoot in the time domain response. If sockets are necessary, flush-mount socket pins are recommended. The device holes in the 730055 evaluation board are sized for Cambion P/N 450-2598 socket pins, or their functional equivalent. Equation 2: Noise Figure Equation The noise figure is related to the equivalent source resistance (Rseq) and the parallel combination of Rf and Rg. To minimize noise figure, the following steps are recommended: Applications Circuits • Minimize RfIIRg • Choose the optimum Rs (ROPT) Transimpedance Amplifier The low 2.5pA/√Hz input current noise and unity gain stability make the CLC440 an excellent choice for transimpedance applications. Figure 3 illustrates a low noise transimpedance amplifier that is commonly implemented with photo diodes. Rf sets the transimpedance gain. The photo diode current multiplied by Rf determines the output voltage. ROPT is the point at which the NF curve reaches a minimum and is approximated by: e ROPT ≅ n in Figure 2 is a plot of NF vs Rs with Rf = 0, Rg = ∞ (Av = +1). The NF curves for both Unterminated and Terminated systems are shown. The Terminated curve assumes Rs = RT. The table indicates the NF for various source resistances including Rs = ROPT. Cf Rf Photo Diode Representation Layout Considerations A proper printed circuit layout is essential for achieving high frequency performance. National provides evaluation boards for the CLC440 (CLC730055-DIP, CLC730060-SOIC) and suggests their use as a guide for high frequency layout and as an aid in device testing and characterization. Iin Cd - Vout CLC440 + Vout = -Iin*Rf Figure 3: Transimpedance Amplifier Configuration 5 http://www.national.com The capacitances are defined as: Rectifier The large bandwidth of the CLC440 allows for high speed rectification. A common rectifier topology is shown in Figure 6. R1 and R2 set the gain of the rectifier. Vout for a 5MHz, 2Vpp sinusoidal input is shown in Figure 7. • Cin = Internal Input Capacitance of the CLC440 • • (typ 1.2pF) Cd = Equivalent Diode Capacitance Cf = Feedback Capacitance D1 The transimpedance plot in the typical performance section provides the recommended Cf and expected bandwidth for different gains and diode capacitances. The feedback capacitances indicated on the plot give optimum gain flatness and stability. If a smaller capacitance is used, then peaking will occur. The frequency response shown in Figure 4 illustrates the influence of the feedback capacitance on gain flatness. D2 R2 R1 Vin Vout CLC440 + Transimpedance Amplifier Frequency Response Figure 6: Rectifier Topology 80 Cf = 0 Rectifier Output Cf = 1pF 2.0 Cf = 2pF 60 1.6 1.2 Cf = 2.5pF 50 0.8 Cf = 5pF Cf 40 Vout (V) Gain (dB) 70 1k - 30 + 100Ω -0.8 20 100k 10k 0 -0.4 CLC440 5pF Iin 0.4 10M 1M 100M -1.2 1G -1.6 Frequency (Hz) -2.0 0 100 400 500 Time (ns) The total input current noise density (ini) for the basic transimpedance configuration is shown in Equation 3. The plot of current noise density versus feedback resistance is shown in Figure 5. Figure 7: Rectifier Output Tunable Low Pass Filter The center frequency of the low pass filter (LPF) can be adjusted by varying the CLC522 gain control voltage, Vg. Current Noise Density vs. Feedback Resistance Current Noise Density (pA/√Hz) 300 200 Figure 4 40 Ra Rf - 35 Rg CLC522 30 + (Total) ini 20Ω 25 RT Vg 20 en Rf 15 R1 if Vin 10 Rin 5 C2 C1 R CLC440 R2 + CLC440 Vout + in 0 1.0 0.1 10 ωo = Feedback Resistance (kΩ) k R1R 2C1C2 RC2 Q= k R1R2C1C2 Rg = Vin (max) 1.8mA A v (max) = k = 1.85 Figure 5 Figure 8: Tunable Low Pass Filter 2 e 2 4kT ini = in + n + Rf Rf Equation 3: Total Equivalent Input Referred Current Noise Density http://www.national.com 6 Rf Rg This page intentionally left blank. 7 http://www.national.com CLC440 High-Speed, Low-Power, Voltage Feedback Op Amp Customer Design Applications Support National Semiconductor is committed to design excellence. For sales, literature and technical support, call the National Semiconductor Customer Response Group at 1-800-272-9959 or fax 1-800-737-7018. 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