TL026C DIFFERENTIAL HIGH-FREQUENCY AMPLIFIER WITH AGC SLFS007A – JUNE 1985 – REVISED JULY 1990 D D D D D D Low Output Common-Mode Sensitivity to AGC Voltages Input and Output Impedances Independent of AGC Voltage Peak Gain . . . 38 dB Typ Wide AGC Range . . . 50 dB Typ 3-dB Bandwidth . . . 50 MHz Other Characteristics Similar to NE592 and uA733 D OR P PACKAGE (TOP VIEW) IN+ AGC VCC OUT+ 1 8 2 7 3 6 4 5 IN– REF OUT VCC+ OUT– symbol AGC description IN + IN – This device is a monolithic two-stage highfrequency amplifier with differential inputs and outputs. 2 7 1 4 8 + – 5 REF OUT OUT+ OUT– Internal feedback provides wide bandwidth, low phase distortion, and excellent gain stability. Variable gain based on signal summation provides large AGC control over a wide bandwidth with low harmonic distortion. Emitter-follower outputs enable the device to drive capacitive loads. All stages are current-source biased to obtain high common-mode and supply-voltage rejection ratios. The gain may be electronically attenuated by applying a control voltage to the AGC pin. No external compensation components are required. This device is particularly useful in TV and radio IF and RF AGC circuits, as well as magnetic-tape and disk-file systems where AGC is needed. Other applications include video and pulse amplifiers where a large AGC range, wide bandwidth, low phase shift, and excellent gain stability are required. The TL026C is characterized for operation from 0°C to 70°C. absolute maximum ratings over operating free-air temperature range (unless otherwise noted)† Supply voltage, VCC+ (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 V Supply voltage, VCC– (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 8 V Differential input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 5 V Common-mode input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 6 V Output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±10 mA Continuous total dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Dissipation Rating Table Operating free-air temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to 70°C Storage temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 65°C to 150°C Lead temperature range 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C † Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. This is a stress rating only, and functional operation of the device at these or any other conditions beyond those indicated in the recommended operating conditions section of this specification is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. NOTE 1: All voltages are with respect to the midpoint of VCC+ and VCC – except differential input and output voltages. DISSIPATION RATING TABLE PACKAGE TA ≤ 25°C POWER RATING OPERATING FACTOR ABOVE TA = 25°C TA = 70°C POWER RATING D 725 mW 5.8 mW/°C 464 mW P 1000 mW 8.0 mW/°C 640 mW Copyright 1990, Texas Instruments Incorporated PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1 TL026C DIFFERENTIAL HIGH-FREQUENCY AMPLIFIER WITH AGC SLFS007A – JUNE 1985 – REVISED JULY 1990 recommended operating conditions MIN NOM MAX Supply voltage, VCC + 3 6 8 Supply voltage, VCC – –3 –6 –8 V 70 °C Operating free-air temperature range, TA 0 UNIT V electrical characteristics at 25°C operating free-air temperature, VCC+ = ±6 V, VAGC = 0, REF OUT pin open (unless otherwise specified) PARAMETER FIGURE TEST CONDITIONS MIN TYP MAX UNIT 65 85 105 V/V AVD Large-signal differential voltage amplification 1 VO(PP) = 3 V, ∆AVD Change in voltage amplification 1 VIPP = 28.5 mV, RL = 2 kΩ, VAGC – Vref = ±180 mV Vref Voltage at REF OUT BW Bandwidth (– 3 dB) IIO IIB Input offset current 0.4 5 µA Input bias current 10 30 µA VICR VOC Common-mode input voltage range 3 Common-mode output voltage 1 RL = ∞ ∆VOC VOO Change in common-mode output voltage 1 Output offset voltage 1 VAGC = 0 to 2 V, VID = 0, VO(PP) Maximum peak-to-peak output voltage swing 1 RL = 2 kΩ ri Input resistance at AGC, IN+, or IN – ro Output resistance CMRR Common mode rejection ratio Common-mode 3 VIC = ±1 V, VIC = ±1 V, kSVR Supply voltage rejection ratio (∆VCC / ∆VIO) 4 ∆VCC + = ± 0.5 V, ∆VCC – = ± 0.5 V Vn tpd Broadband equivalent noise voltage 4 Propagation delay time 2 tr Isink(max) Rise time 2 ICC Supply current 2 Maximum output sink current 2 RL = 2 kΩ Iref = – 1 mA to 100 µA VO(PP) = 1 V, VAGC – Vref = ±180 mV – 50 1.3 dB 1.5 50 MHz ±1 3.25 V V 4.25 V RL = ∞ 300 mV RL = ∞ 0.75 V f = 100 kHz 3.75 3 4 V 10 30 kΩ 20 Ω 60 f = 5 mHz 86 dB 60 70 dB BW = 1 kHz to 10 MHz 12 µV ∆VO = 1 V ∆VO = 1 V 6 10 ns 4.5 12 ns VID = 1 V, No load, POST OFFICE BOX 655303 50 VO = 3 V No signal • DALLAS, TEXAS 75265 3 4 22 mA 27 mA TL026C DIFFERENTIAL HIGH-FREQUENCY AMPLIFIER WITH AGC SLFS007A – JUNE 1985 – REVISED JULY 1990 electrical characteristics over recommended operating free-air temperature range, VCC ± = ± 6 V, VAGC = 0, REF OUT pin open (unless otherwise specified) PARAMETER FIGURE UNIT 115 V/V 6 µA IIB VICR Input bias current 40 µA Common-mode input voltage range 3 VOO VO(PP) Output offset voltage 1 Maximum peak-to-peak output voltage swing 1 ri Input resistance at AGC, IN+, or IN – CMRR Common-mode rejection ratio 3 kSVR Supply voltage rejection ratio (∆VCC / ∆VIO) 4 1 55 MAX Input offset current Supply current RL = 2 kΩ TYP Large-signal differential voltage amplification Maximum output sink current VO(PP) = 3 V, MIN AVD IIO Isink(max) ICC 1 TEST CONDITIONS ±1 VID = 0, RL = 2 kΩ V RL = ∞ 1.5 V 2.8 V 8 kΩ VIC = ±1 V, f = 100 kHz ∆VCC + = ± 0.5 V, ∆VCC – = ± 0.5 V 50 dB 50 dB VID = 1 V, No load, 2.8 VO = 3 V No signal 4 mA 30 mA PARAMETER MEASUREMENT INFORMATION REF OUT AGC VAGC Vref IN + 0.2 µF + OUT + VOD VID 50 Ω VID RL – IN – + V + OC V O ) ) VO * 50 Ω 50 Ω VO – 1 kΩ 1 kΩ 2 Figure 1. Test Circuit Figure 2. Test Circuit 0.2 µF 50 Ω + VO + + 0.2 µF 50 Ω – VIC 0.2 µF – OUT – 50 Ω VO + VO – 1 kΩ VOD RL = 2 kΩ – 1 kΩ Figure 3. Test Circuit Figure 4. Test Circuit POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 3 TL026C DIFFERENTIAL HIGH-FREQUENCY AMPLIFIER WITH AGC SLFS007A – JUNE 1985 – REVISED JULY 1990 TYPICAL CHARACTERISTICS AVD — Differential Voltage Amplification — V/ V DIFFERENTIAL VOLTAGE AMPLIFICATION vs DIFFERENTIAL GAIN-CONTROL VOLTAGE 100 VCC + = 6 V VCC – = – 6 V 90 80 70 60 TA = 0°C TA = 25°C TA = 70°C 50 40 30 20 10 0 – 200 – 100 0 100 200 VAGC – Vref – Differential Gain-Control Voltage – mV Figure 5 4 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TL026C DIFFERENTIAL HIGH-FREQUENCY AMPLIFIER WITH AGC SLFS007A – JUNE 1985 – REVISED JULY 1990 APPLICATION INFORMATION gain characteristics Figure 5 shows the differential voltage amplification versus the differential gain-control voltage (VAGC – Vref). VAGC is the absolute voltage applied to the AGC input and Vref is the dc voltage at the REF OUT output. As VAGC increases with respect to Vref, the TL026C gain changes from maximum to minimum. As shown in Figure 5 for example, VAGC would have to vary from approximately 180 mV less than Vref to approximately 180 mV greater than Vref to change the gain from maximum to minimum. The total signal change in VAGC is defined by the following equation. ∆VAGC = Vref + 180 mV – (Vref – 180 mV) (1) ∆VAGC = 360 mV However, because VAGC varies as the ac AGC signal varies and also differentially around Vref, then VAGC should have an ac signal component and a dc component. To preserve the dc and thermal tracking of the device, this dc voltage must be generated from Vref. To apply proper bias to the AGC input, the external circuit used to generate VAGC must combine these two voltages. Figures 6 and 7 show two circuits that will perform this operation and are easy to implement. The circuits use a standard dual operational amplifier for AGC feedback. By providing rectification and the required feedback gain, these circuits are also complete AGC systems. circuit operation Amplifier A1 amplifies and inverts the rectified and filtered AGC signal voltage VC producing output voltage V1. Amplifier A2 is a differential amplifier that inverts V1 again and adds the scaled Vref voltage. This conditioning makes VAGC the sum of the signal plus the scaled Vref. As the signal voltage increases, VAGC increases and the gain of the TL026C is reduced. This maintains a constant output level. feedback circuit equations Following the AGC input signal (Figures 6 and 7) from the OUT output through the feedback amplifiers to the AGC input produces the following equations: 1. AC ouput to diode D1, assuming sinusoidal signals VO = VOP (sin (wt)) where: VOP = peak voltage of VO 2. Diode D1 and capacitor C1 output VC = VOP – VF where: VF = forward voltage drop of D1 VC = voltage across capacitor C1 (2) (3) 3. A1 output R2 V V1 R1 C +* (4) 4. A2 output (R3 = R4) V AGC + R2 R1 VC ) 2 R5 R6 ) R6 (5) V ref POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 5 TL026C DIFFERENTIAL HIGH-FREQUENCY AMPLIFIER WITH AGC SLFS007A – JUNE 1985 – REVISED JULY 1990 APPLICATION INFORMATION Amplifier A2 inverts V1 producing a positive AGC signal voltage. Therefore, the input voltage to the TL026C AGC pin consists of an AGC signal equal to: R2 V R1 C (6) and a dc voltage derived from Vref, defined as the quiescent value of VAGC. V AGC(q) + 2 R5 R6 ) R6 Vref (7) For the initial resistor calculations, Vref is assumed to be typically 1.4 V making quiescent VAGC approximately 1.22 V (VAGC(q) = Vref – 180 mV). This voltage allows the TL026C to operate at maximum gain under no-signal and low-signal conditions. In addition, with Vref used as both internal and external reference, its variation from device to device automatically adjusts the overall bias and makes AGC operation essentially independent of the absolute value of Vref. The resistor divider needs to be calculated only once and is valid for the full tolerance of Vref. output voltage limits (see Figures 6 and 7) The output voltage level desired must fall within the following limits: 1. Because the data sheet minimum output swing is 3 V peak-to-peak using a 2-kΩ load resistor, the user-selected design limit for the peak output swing should not exceed 1.5 V. 2. The voltage drop of the rectifying diode determines the lower voltage limit. When a silicon diode is used, this voltage is approximately 0.7 V. The output voltage VO must have sufficient amplitude to exceed the rectifying diode drop. Aschottky diode can be used to reduce the VO level required. gain calculations for a peak output voltage of 1 V A peak output voltage of 1 V was chosen for gain calculations because it is approximately midway between the limits of conditions 1 and 2 in the preceding paragraph. Using equation 3 (VC = VOP – Vd), VC is calculated as follows: VC = 1 V – 0.7 V VC = 0.3 V Therefore, the gain of A1 must produce a voltage V1 that is equal to or greater than the total change in VAGC for maximum TL026C gain change. With a total change in VAGC of 360 mV and using equation 4, the calculation is as follows: * VV1 + DVVAGC + R2 + 0.36 + 1.2 0.3 R1 C C If R1 is 10 kΩ, R2 is 1.2 time R1 or 12 kΩ. Since the output voltage for this circuit must be between 0.85 V and 1.3 V, the component values in Figures 6 and 7 provide a nominal 1-V peak output limit. This limit is the best choice to allow for temperature variations of the diode and minimum output voltage specification. 6 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TL026C DIFFERENTIAL HIGH-FREQUENCY AMPLIFIER WITH AGC SLFS007A – JUNE 1985 – REVISED JULY 1990 APPLICATION INFORMATION The circuit values in Figures 6 and 7 will produce the best results in this general application. Because of rectification and device input constraints, the circuit in Figure 6 will not provide attenuation and has about 32 dB of control range. The circuit shown in Figure 7 will have approximately 25% variation in the peak output voltage limit due to the variation in gain of the TL592 device to device. In addition, if a lower output voltage is desired, the output of the TL026C can be used for approximately 40 mV of controlled signal. considerations for the use of the TL026C To obtain the most reliable results, RF breadboarding techniques must be used. A groundplane board should be used and power supplies should be bypassed with 0.1-µF capacitors. Input leads and output leads should be as short as possible and separated from each other. A peak input voltage greater than 200 mV will begin to saturate the input stages of the TL026C and, while the circuit is in the AGC mode, the output signal may become distorted. To observe the output signal of TL026C or TL592, low-capacitance FET probes or the output voltage divider technique shown in Figure 6 should be used. TL026C IN – VI 50 Ω IN + – + 50 Ω AGC OUT + 0.1 µF Vout 1.8 kΩ OUT – REF OUT 0.1 µF 200 Ω 12 kΩ 30 kΩ 10 kΩ 10 kΩ A1 V1 A2 + 1/2 TL082 1N914 D1 – 10 kΩ – VAGC To Scope Monitor + 0.1 µF 1/2 TL082 20 kΩ NOTE: VCC + = 6 V and VCC – = – 6 V for TL026C and amplifiers A1 and A2. Figure 6. Typical Application Circuit With No Attenuation POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 7 TL026C DIFFERENTIAL HIGH-FREQUENCY AMPLIFIER WITH AGC SLFS007A – JUNE 1985 – REVISED JULY 1990 APPLICATION INFORMATION 1N914 R1 R2 R3 R4 10 kΩ 12 kΩ 10 kΩ 10 kΩ 1/2 TL082 0.1 µF 1/2 TL082 – – A1 + + 30 kΩ VOUT – 0.1 µF VOUT + 0.1 µF OUT – – X20 Gain + TL592 1.8 kΩ To Scope Monitor OUT + TL026C IN – – + 2 kΩ AGC 2 kΩ NOTE: VCC + = 6 V and VCC – = – 6 V for TL026C and amplifiers A1 and A2. Figure 7. Typical Application Circuit With Attenuation POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 VI 50 Ω IN + 200 Ω 8 R6 20 kΩ REF OUT 510 Ω 0.1 µF VAGC A2 R5 50 Ω IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. 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