Powerful and feature-packed, the Pure Resonance Audio RZMA120BT is a multi zone mixer amplifier featuring 4 x 120-watt output capability at 4 Ohm, 70 and 100 Volts. A large capacitor (not shown) is coupled to terminal 55 to hold the impedance at the bases of the current-source transistors Q245/246 to as low a value as possible minimizing HF modulation noise. 5 graphically illustrates the impedance change of the LO bias circuit. In addition, by applying the L0 signal and the gain change signal to a variable gain mixer having only two gains at the same time, a gain change with linearity in dB characteristics is possible. The differential voltage between MH and ML is transferred via the emitter-followers Q256 through Q259 to the bases of Q266 and Q267 in the R241 branch and the bases of Q262 and Q263 in the R240 branch, respectively. Having described and illustrated the principles of the invention in a preferred embodiment thereof, it should be apparent that the invention can be modified in arrangement and detail without departing from such principles. The Variable Gain Amplifiers are used in a variety of Network, Commercial and Aerospace and Defense applications. IC ", International Solid-State Circuits and Systems, 2002, 14.5). Thus, the nominal collector current of Q245 and Q246 is 7*l09 μA or approximately 763 μA. The signal is then mixed to the LO to perform frequency translation. The mixer section 36, in addition to embodying a transconductance stage, includes a linear-in-dB gain control circuit that varies the gain of the mixer exponentially in response to linear changes in a gain control current (IG) applied to terminal 54. Double Balanced Mixer Operating from 2 GHz to 18 GHz with an IF … Thus, a linear increase in IG causes an exponential reduction in the transconductance gm at the input stage of the mixer core 42, i.e., a logarithmic gain reduction is produced. In the preferred embodiment, the mixer circuit 30 is implemented in complementary bipolar technology. Flexibile solution: Variable gain switch: -10/-20dB, -15/-25dB or -25/-35dB read more…. The scaling is chosen such that a 1 μA (PTAT) change in IG causes ΔVBE of 1 mV (PTAT) and consequently a change of exp(1/26), or about 0.333 dB in the mixer's gain. a PNP transistor having a base connected to the cathode of the second diode, a collector coupled to a common supply terminal, and an emitter coupled to the emitter of the NPN transistor. In one embodiment, R235 and R236 are each approximately 458.5 ohms. frequency-changing by means of semiconductor devices having more than two electrodes, Balanced arrangements with transistors using bipolar transistors, Double balanced arrangements, i.e. The multi-tanh doublet is described in my commonly-assigned, co-pending application entitled "LOW-SUPPLY VOLTAGE MIXER HAVING OVERLAPPING INPUT SIGNAL RANGES," Ser. Now you’re getting the strongest signal form the keyboard and with the mixer gain turned down, you’ll get the control you need. The variable gain mixer of claim 1 wherein the two pairs of transistors, Qp + / Qn + and Qp− / Qn−, each form a current regulated variable gain amplifier. However, more current is then required to remove the charge from the base of Q1, which makes this approach difficult to implement for high frequency applications. The second amplifier stage supplies a loaded low frequency gain of approximately 30.3. Figure 2 illustrates an embodiment of a conventional current regulated variable gain amplifier. The AC measurements show that chopping removes not only offset, but also noise and second-order harmonic distortion. A method includes controlling a mixer gain to provide a range of selected power output levels from the mixer using a first control scheme for a low portion of the range and using a second control scheme for a high portion of the range. a second current source coupled to the cathode of the first diode-connected transistor. Complete Patent Searching Database and Patent Data Analytics Services. Our VGA Product family covers frequencies from 5 MHz to 20 GHz. Thus, the 75 μA (PTAT) full-scale change in IG (2 μA to 77 μA) results in a gain change of 75*0.333 dB, or 25 dB. The voltages at the emitters of diodes Q258 and Q259 are sensed by the PNP emitter followers Q254 and Q255, and averaged in R238 and R239, in conjunction with C257. a second branch transistor having a collector coupled to the voltage supply terminal, a base coupled to the second mixer output, and an emitter coupled to the anode of the second diode, the second branch transistor producing a second current that passes through the second diode responsive to the signal on the second mixer output. The low-pass corner attenuates the sum frequency component of the output signal, typically of 240 MHZ+229.3 MHz=469.3 MHz, while the intermediate frequency (IF) present between terminals 74 and 76 is passed with little attenuation. A similar but complementary design is used in current mirror 80. a first gain control transistor having a base, a collector coupled to a bias node for receiving a bias current, and an emitter coupled to a common supply rail; a second gain control transistor having a base coupled to the collector of the first gain control transistor, a collector coupled to a positive supply rail, and an emitter coupled to a gain control input of the mixer; a first resistor coupled between the base of the first gain control transistor and the gain control circuit input; a second resistor coupled between the gain control circuit input and the gain control input of the mixer for providing a gain control output signal thereto; and. If you are setting the gain on a channel that is running to external processing, such as a compressor or EQ, you should bypass them all before setting the gain. © 2004-2021 FreePatentsOnline.com. By applying LO to Qn + and Qn-, a constant base voltage difference can be maintained even when the LO signal level is high, and the variable gain mixer VGM does not depend on the LO signal level. However, the current is not doubled because of the inclusion of the emitter resistors R240 and R241. FIG. an input transistor having a collector coupled to the collector of the first NPN transistor, an emitter coupled to the positive supply rail, and a base; an output transistor having a base coupled to the base of the input transistor, an emitter coupled to the positive supply rail, and a collector coupled to the output of the post-mixer linearizer; a drive transistor having an emitter coupled to the base of the output transistor for receiving a drive current, a collector coupled to a common supply rail, and a base; and. The change in primary current to Q235 is especially problematic for very low betas. Should a small DC offset voltage be present at the RF port (e.g., due to a mismatch in the emitter areas of Q5 and Q6), this will only result in a small feed through of the LO signal VLO to the IF output port, which will be blocked by a first IF filter (not shown). How to Set Gain on an Analog Mixer. Double Balanced Mixer Operating from 2 GHz to 18 GHz with an IF Range from DC to 600 MHz and LO Power of +10 dBm, SMA from Pasternack has same day shipment. a first current mirror coupled to the collector of the first NPN transistor and the output of the post-mixer linearizer, the first current mirror providing a first mirrored current to the post-mixer linearizer output that is proportional to the collector current in the first NPN transistor; and. Solutions are available in both dual mixer and single mixer configurations. A practical mixer will have higher losses, due to the resistances of the diodes and the losses in the transformers. R207 co-balances the bias offset created by R208 and capacitor C201 shunts R207 at high frequencies. The Variable Gain Amplifiers are used in a variety of Network, Commercial and Aerospace and Defense applications. If the collector current of Q + is expressed as Ioutp and the collector current of Q- is expressed as Ioutn, Iout = Ioutp-Ioutn and the output signal. Using this capability, an active mixer can provide variable gain. If a 328 mV variation is superimposed on a VBE drop, the collectors in the mixer core fall by a maximum of about 1 V below VP. No. To reduce noise bursts 28, the mixer core transistors need to be turned on more quickly to supply more charge to their base terminals. a mixer including a first input for receiving a first input signal, a second input for receiving a second input signal, and first and second differential outputs for providing a differential mixed output signal thereacross that is the product of the first signal and the second signal, the mixer having a linear transconductance within a given operating range and a nonlinear transconductance outside the given operating range; and, a post-mixer linearizer circuit having a first input coupled to the first differential output of the mixer, a second input coupled to the second differential output of the mixer, and an output for providing an output signal having improved linearity, wherein the post-mixer linearizer includes. AD9850 Module. 4 is a block diagram of a mixer circuit according to the invention. Passive and active mixers are distinguished by the fact that active mixers provide a positive conversion gain, whereas passive mixers do not. The output stages are biased to moderate currents, but the transistors Q219-222 carry high peak currents of about 400 μA at a typical LO frequency of 229 MHz due to the base-current loading of the mixer's core (FIG. The current mirrors 80 and 82 satisfy these two objectives. Capacitor C202 ensures that the beta-loop around Q223 and Q224 is stable, and also maintains a low impedance at high frequency. The current gain is determined by equation (2). In order to achieve the linear-in-dB characteristic, it is necessary to apply the LO signal to both Qn +-and Qp +-. The first amplifier stage is biased by a current mirror comprised of transistors Q201 and Q202. A 2–10 GHz Gilbert-type mixer is reported in which the gate widths of the transistors in the RF stage are reconfigurable. 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