DC to 8GHz Simple Amplifiers
The availability of RF Monolithic amplifiers allowed designers to focus on the subsystem specifications instead of on the design of the individual amplifiers. The same design convenience became available to microwave frequencies with the introduction of Mini Circuit's ERA amplifiers. The ERA series include ERA1, ERA2, ERA3, ERA4, and ERA5.The units are available in drop-in and surface mount packages.The 50 ohm amplifiers provide excellent gain up to 8GHz and beyond, and are usable up to 10GHz
Electrical Performance
The ERA series amplifiers have excellent dynamic range for small, inexpensive monolithic amplifiers. An amplifier's dynamic range is determined by its maximum output power (1-dB compression point) at the high end and by its noise figure at the low end. The two-tone third-order intercept point (IP3) is another measure of the linearity of an amplifier. The ERA-1 has a noise figure of 7dB typical, a 1-dB compression point at 13dBm typical, and an IP3 of 26 dBm typical. The ERA-2 has a noise figure of 6dB typical, a 1-dB compression point at 14dBm typical, and an IP3 of 27dBm typical.The ERA-3 has a better noise figure of 4.5 dB typical, with a slightly lower 1-dB compression point at 11dBm, and an IP3 of 23 dBm typical.The ERA-4 has a noise figure of 5.2 dB typical, a higher 1-dB compression point at 19dB and a higher IP3 of 35dBm typical. The ERA-5 has a noise figure of 4dB typical, a higher 1-dB compression point at 19.2 dBm typical, and an excellent IP3 of 35dBm typical. The 1-dB compression points, noise figures,and IP3 values stated are measured at 2GHz.
The ERA series amplifiers are designed for use in 50 ohm systems. All of the ERA amplifiers typically have an input VSWR of 1.8:1 up to 2 GHz and 2.2:1 above the 2GHz.The typical VSWR is 1.9:1 below 2Ghz and 2.2:1 above 2GHz.
| Model | Freq. (MHz) | dBm output @ 1-dB compression point | NF (dB) | GAIN (dB) | IP3 (dBm) | Price $each |
| ERA-1 | DC-8000 | 13.0 | 7.0 | 11.6 | 26 | 1.80 |
| ERA-1SM | DC-8000 | 13.0 | 7.0 | 11.0 | 26 | 1.85 |
| ERA-2 | DC-6000 | 14.0 | 6.0 | 14.9 | 27 | 1.95 |
| ERA-2SM | DC-6000 | 13.0 | 6.0 | 13.1 | 27 | 2.00 |
| ERA-3 | DC-3000 | 11.0 | 4.5 | 20.2 | 23 | 2.10 |
| ERA-3SM | DC-3000 | 11.0 | 4.5 | 19.4 | 23 | 2.15 |
| ERA-4 | DC-4000 | 19.1 | 5.2 | 13.9 | 36 | 4.15 |
| ERA-4SM | DC-4000 | 19.1 | 5.2 | 13.9 | 36 | 4.20 |
| ERA-5 | DC-4000 | 19.6 | 4.0 | 19.0 | 36 | 4.15 |
| ERA-5SM | DC-4000 | 19.4 | 4.0 | 19.0 | 36 | 4.20 |
Biasing the ERA Amplifiers
The ERA amplifiers require several external components to bias them correctly. In a typical circuit, blocking capacitors are used at the input and output of the amplifier. An RF choke in the 2.2uH range should be used at higher frequencies to block the RF from traveling through the DC supply. A bias resistor is used between the DC supply voltage and the bias terminal of the amplifier, the bias resistor appears in parallel with the 50 ohm output load.If the resistance of the bias resistor is not sufficiently large (500 ohms or greater), a significant amount of RF power can flow through the bias resistor. This could reduce the effective gain and output power of the asmplifier and an increase in the output VSWR. If the choke is added it will prevent this situation.Thr RF choke should have a reactance of at least 500 ohms at the lowest RF frequency that will be seen by the amplifier. The value of the biasing resistor depends on the supply voltage used. The value can be calculated from:
Rbias= 1000(Vcc -Vd)Ibias
Where Vcc = the supply voltage
Vd = the device bias voltage ( 3.8 volts for ERA-1, ERA-2, ERA-3 and 5.0volts for ERA-4, ERA-5)
Ibias = the bias current in mA( 50mA for ERA-1,ERA-2. 35mA for ERA-3. 80mA for ERA-4, ERA-5.)
Junction Temperature and Reliability
The ERA series amplifiers have an operating temperature of -25 to +85 oC. The maximum case temperature is 200 oC. The reliability of the ERA series depends on the maximum junction temperature of the MMIC. The junction temperature depends on the device operating temperature. The junction temperature for the ERA amplifiers is determined using the following formula:
Tj = Tamb +(Pd x Ojc)
Tj = the junction temperature in oC
Tamb = the ambient temperature in oC
Pd = power dissipated by the amplifier in W
Ojc = the thermal resistance from the junction to the case in oC/W
For example, consider the MTTF of the ERA-3 at 85o C ambient temperature. For the ERA-3, Pd=0.035 x 3.8V=0.133W and 0jc=432 oC/W. The junction temperature at an 85oC ambient temperature is therefore:
Tj = 85 + (0.133 x 432) = 142 oC
At a 142 C junction temperature, the ERA amplifiers have a mean time to failure (MTTF) of several hundred years. At 25 C ambient temperature the ERA-3 has an MTTF of 1000 years.
(Back to Page)